2013 iMac started suddenly shutting down

My Late 2012 27" iMac (bought in 2013) has suddenly started shutting down with no warning. The only way to start it again is to unplug the mains cord and wait a few minutes and plug it back in. The shutdowns are completely random. I have run EtreCheck, and below is the report. I can't see anything obvious myself that is causing the issue. Has anyone any idea as to what is causing this? There are lots of other people reporting the same problem, with no definitive solution.

EtreCheck version: 2.9.10 (261)

Report generated 2016-04-07 19:51:06

Download EtreCheck from https://etrecheck.com

Runtime 2:41

Performance: Excellent

Click the [Support] links for help with non-Apple products.

Click the [Details] links for more information about that line.

Problem: Other problem

Description:

Mac shuts down without warning. Won’t re-start until it’s been left a while.

Hardware Information: ⓘ

iMac (27-inch, Late 2012)

[Technical Specifications] - [User Guide] - [Warranty & Service]

iMac - model: iMac13,2

1 3.4 GHz Intel Core i7 CPU: 4-core

24 GB RAM Upgradeable - [Instructions]

BANK 0/DIMM0

4 GB DDR3 1600 MHz ok

BANK 1/DIMM0

4 GB DDR3 1600 MHz ok

BANK 0/DIMM1

8 GB DDR3 1600 MHz ok

BANK 1/DIMM1

8 GB DDR3 1600 MHz ok

Bluetooth: Good - Handoff/Airdrop2 supported

Wireless: Unknown

Video Information: ⓘ

NVIDIA GeForce GTX 680MX - VRAM: 2048 MB

iMac 2560 x 1440

BenQ G2410HD 1920 x 1080 @ 60 Hz

System Software: ⓘ

OS X El Capitan 10.11.3 (15D21) - Time since boot: less than an hour

Disk Information: ⓘ

APPLE HDD ST1000DM003 disk1 : (1 TB) (Rotational)

EFI (disk1s1) <not mounted> : 210 MB

Recovery HD (disk1s3) <not mounted> [Recovery]: 650 MB

Macintosh HD (disk2) / : 1.11 TB (729.40 GB free)

Core Storage: disk0s2 120.99 GB Online

Core Storage: disk1s2 999.35 GB Online

APPLE SSD SM128E disk0 : (121.33 GB) (Solid State - TRIM: Yes)

EFI (disk0s1) <not mounted> : 210 MB

Boot OS X (disk0s3) <not mounted> : 134 MB

Macintosh HD (disk2) / : 1.11 TB (729.40 GB free)

Core Storage: disk0s2 120.99 GB Online

Core Storage: disk1s2 999.35 GB Online

USB Information: ⓘ

Apple, Inc. Keyboard Hub

Logitech USB Receiver

Fitbit Inc. Fitbit Base Station

Apple Inc. Apple Keyboard

Apple Inc. FaceTime HD Camera (Built-in)

Apple Inc. BRCM20702 Hub

Apple Inc. Bluetooth USB Host Controller

VLI Labs, Inc. USB 3.0 HUB

VLI Labs, Inc. USB 3.0 HUB

HGST Touro Mobile 3.0 1 TB

EFI (disk3s1) <not mounted> : 210 MB

Backup (disk3s2) /Volumes/Backup : 999.86 GB (82.13 GB free)

VIA Labs, Inc. USB3.0 Hub 64.02 GB

Lexar USB Flash Drive 64.02 GB

Lexar (disk4s1) /Volumes/Lexar : 64.02 GB (26.19 GB free)

MediaTek Inc MT1956

VIA Labs, Inc. USB2.0 Hub

Thunderbolt Information: ⓘ

Apple Inc. thunderbolt_bus

Configuration files: ⓘ

/etc/sysctl.conf - File exists but not expected

/etc/hosts - Count: 2

Gatekeeper: ⓘ

Mac App Store and identified developers

Kernel Extensions: ⓘ

/Applications/AVG AntiVirus.app

[loaded] com.avg.Antivirus.OnAccess.kext (2015.0 - SDK 10.8 - 2016-04-07) [Support]

/Applications/MacX Video Converter Pro.app

[not loaded] com.macxdvd.driver.goodSysAudioCapture (1 - SDK 10.10 - 2015-05-22) [Support]

/Applications/Parallels Desktop.app

[not loaded] com.parallels.kext.hypervisor (11.1.2 32408 - SDK 10.9 - 2016-02-13) [Support]

[not loaded] com.parallels.kext.netbridge (11.1.2 32408 - SDK 10.9 - 2016-02-13) [Support]

[not loaded] com.parallels.kext.usbconnect (11.1.2 32408 - SDK 10.9 - 2016-02-13) [Support]

[not loaded] com.parallels.kext.vnic (11.1.2 32408 - SDK 10.9 - 2016-02-13) [Support]

/Applications/Toast 12 Titanium/Toast Titanium.app

[not loaded] com.roxio.TDIXController (2.0 - 2016-02-06) [Support]

/Library/Extensions

[loaded] com.Logitech.Control Center.HID Driver (3.9.1 - SDK 10.8 - 2016-04-05) [Support]

[loaded] com.Logitech.Unifying.HID Driver (1.3.1 - SDK 10.8 - 2016-04-05) [Support]

[loaded] com.globaldelight.driver.Boom2Device (1.1 - SDK 10.10 - 2016-04-05) [Support]

[loaded] com.globaldelight.driver.BoomDevice (1.3 - SDK 10.9 - 2016-04-05) [Support]

/System/Library/Extensions

[not loaded] com.Greatdy.driver.SystemAudioCapture (1.0.0 - SDK 10.8 - 2016-04-05) [Support]

[not loaded] com.livescribe.kext.LivescribeSmartpen (1 - 2016-04-05) [Support]

[not loaded] com.makemkv.kext.daspi (1.5 - 2016-04-05) [Support]

[not loaded] com.nike.sportwatch (1.0.0 - 2016-04-05) [Support]

[loaded] com.nvidia.CUDA (1.1.0 - 2016-04-05) [Support]

System Launch Agents: ⓘ

[not loaded] 7 Apple tasks

[loaded] 156 Apple tasks

[running] 73 Apple tasks

System Launch Daemons: ⓘ

[not loaded] 45 Apple tasks

[loaded] 156 Apple tasks

[running] 87 Apple tasks

Launch Agents: ⓘ

[running] com.Logitech.Control Center.Daemon.plist (2014-06-19) [Support]

[not loaded] com.adobe.AAM.Updater-1.0.plist (2015-10-13) [Support]

[running] com.adobe.AdobeCreativeCloud.plist (2015-10-13) [Support]

[failed] com.apple.fonts.plist

[running] com.avg.Antivirus.gui.plist (2014-09-29) [Support]

[running] com.epson.epw.agent.plist (2008-11-14) [Support]

[loaded] com.google.keystone.agent.plist (2016-03-02) [Support]

[running] com.huion.HuionTabletConsole.agent.plist (2014-12-26) [Support]

[loaded] com.nvidia.CUDASoftwareUpdate.plist (2016-04-07) [Support]

[loaded] com.oracle.java.Java-Updater.plist (2013-08-22) [Support]

Launch Daemons: ⓘ

[loaded] com.adobe.SwitchBoard.plist (2013-08-22) [Support]

[running] com.adobe.adobeupdatedaemon.plist (2015-10-13) [Support]

[loaded] com.adobe.agsservice.plist (2015-08-31) [Support]

[loaded] com.adobe.fpsaud.plist (2015-10-15) [Support]

[loaded] com.atlassian.SourceTreePrivilegedHelper2.plist (2014-07-06) [Support]

[running] com.autodesk.backburner_manager.plist (2011-08-31) [Support]

[running] com.autodesk.backburner_server.plist (2011-08-31) [Support]

[loaded] com.autodesk.backburner_start.plist (2011-08-31) [Support]

[loaded] com.avg.Antivirus.crashpad.plist (2015-09-17) [Support]

[running] com.avg.Antivirus.infosd.plist (2014-09-29) [Support]

[running] com.avg.Antivirus.services.plist (2014-09-29) [Support]

[running] com.backblaze.bzserv.plist (2015-11-07) [Support]

[loaded] com.barebones.authd.plist (2013-08-22) [Support]

[loaded] com.cocoatech.pathfinder.SMFHelper7.plist (2015-10-29) [Support]

[running] com.fitbit.galileod.plist (2013-10-22) [Support]

[loaded] com.google.keystone.daemon.plist (2016-03-02) [Support]

[running] com.insynchq.insync.daemon.plist (2014-03-18) [Support]

[running] com.livescribe.PenCommService.plist (2014-11-16) [Support]

[loaded] com.malwarebytes.MBAMHelperTool.plist (2016-03-01) [Support]

[loaded] com.microsoft.autoupdate.helpertool.plist (2016-02-29) [Support]

[loaded] com.microsoft.office.licensing.helper.plist (2015-03-04) [Support]

[loaded] com.nvidia.cuda.launcher.plist (2016-02-03) [Support]

[loaded] com.oracle.java.Helper-Tool.plist (2013-08-22) [Support]

[loaded] com.purevpn.macapp.HelperTool.plist (2015-11-18) [Support]

[loaded] com.sharpcast.xfsmond.plist (2013-11-25) [Support]

[loaded] jp.co.canon.MasterInstaller.plist (2014-08-29) [Support]

User Launch Agents: ⓘ

[loaded] com.adobe.AAM.Updater-1.0.plist (2013-08-22) [Support]

[failed] com.adobe.ARM.[...].plist (2013-08-22) [Support]

[failed] com.amazon.cloud-player.plist (2014-06-12) [Support]

[running] com.amazon.music.plist (2016-04-03) [Support]

[running] com.backblaze.bzbmenu.plist (2016-04-07) [Support]

[failed] com.crashplan.engine.plist (2015-11-04) [Support]

[loaded] com.f-secure.sync.BTCloud.plist (2013-12-20) [Support]

[running] com.spotify.webhelper.plist (2016-04-07) [Support]

User Login Items: ⓘ

CheatSheet Application (/Applications/CheatSheet.app)

iSyncr Application (/Applications/iSyncr.app)

OneTime UNKNOWN (missing value)

Moveslink2 Application (/Applications/Moveslink2.app)

Boom UNKNOWN (missing value)

iTunesHelper Application (/Applications/iTunes.app/Contents/MacOS/iTunesHelper.app)

Dropbox Application (/Applications/Dropbox.app)

Google Drive Application (/Applications/Google Drive.app)

Path Finder Application (/Applications/Path Finder.app)

Android File Transfer Agent Application (~/Library/Application Support/Google/Android File Transfer/Android File Transfer Agent.app)

Espionage UNKNOWN (missing value)

Skype Application (/Applications/Skype.app)

Voila Application (/Applications/Voila.app)

BT Cloud Application (/Applications/BT Cloud.app)

BT Cloud Application (/Applications/BT Cloud.app/Contents/MacOS/BT Cloud.app)

Insync Application (/Applications/Insync.app)

Plex Media Server Application (/Applications/Plex Media Server.app)

Box Sync Application (/Applications/Box Sync.app)

Garmin ANT Agent UNKNOWN (missing value)

Dropzone UNKNOWN (missing value)

Canon IJ Network Scanner Selector EX Application Hidden (/Applications/Canon Utilities/IJ Network Scanner Selector EX/Canon IJ Network Scanner Selector EX.app)

ClipBuddy Application (/Applications/ClipBuddy.app)

AVG AntiVirus Application (/Applications/AVG AntiVirus.app)

Sony Ericsson Bridge Helper Application Hidden (~/Library/Application Support/Sony Ericsson Bridge for Mac/Sony Ericsson Bridge Helper.app)

TweetDeck Application (/Applications/TweetDeck.app)

EvernoteHelper UNKNOWN (missing value)

Livescribe AutoLaunch Application (/Applications/Echo Desktop.app/Contents/MacOS/Pen Auto Launcher.app)

Fitbit Connect Menubar Helper UNKNOWN (missing value)

Spotify Application Hidden (/Applications/Spotify.app)

MagicMenu Application (/Applications/StuffIt Archive Manager.app/Contents/MacOS/MagicMenu.app)

CrashPlan menu bar UNKNOWN (missing value)

CleanMyMac 3 Menu UNKNOWN (missing value)

CrashPlan menu bar UNKNOWN (missing value)

Espionage Application (/Applications/Espionage.app)

EvernoteHelper Application (/Applications/Evernote.app/Contents/Library/LoginItems/EvernoteHelper.app)

Dashlane Application (/Applications/Dashlane.app)

Garmin Express Service Application (/Applications/Garmin Express.app/Contents/Library/LoginItems/Garmin Express Service.app)

Playback Server Application (/Applications/Playback.app/Contents/Resources/Playback Server.app)

MediaFire Desktop Application (/Applications/MediaFire Desktop.app)

MacUpdate Desktop Application Hidden (/Applications/MacUpdate Desktop.app)

Content Manager Assistant UNKNOWN (missing value)

Other Apps: ⓘ

[running] Suunto.Moveslink2.2912

[running] com.JRTStudio.iSyncrWiFi.90912

[running] com.adobe.acc.AdobeDesktopService.248992.AD303842-3011-409C-BBDE-018D87D4389B

[running] com.adobe.accmac.247072

[running] com.aptonic.Dropzone3.73632

[loaded] com.aptonic.LaunchAtLogin

[running] com.box.sync.3232

[running] com.cocoatech.PathFinder.105952

[running] com.dashlane.DashlaneAgent

[loaded] com.dashlane.DashlaneAutoStartHelper

[running] com.etresoft.EtreCheck.467872

[running] com.evernote.EvernoteHelper.101792

[running] com.fsecure.sync.BTCloud.64672

[running] com.garmin.renu.service.82272

[running] com.getdropbox.dropbox.73312

[running] com.globaldelight.VoilaCapture

[running] com.globaldelight.VoilaMAS.125792

[running] com.google.Chrome.85152

[running] com.google.GoogleDrive.85472

[running] com.google.android.mtpagent.148512

[running] com.gopro.GoPro-Studio-GoPro-Importer

[running] com.insynchq.insync.135712

[running] com.macupdate.desktop6.93152

[running] com.mediaatelier.CheatSheet.67872

[running] com.mediafire.desktop.7712

[running] com.ondesoft.clipbuddy.68832

[running] com.plexapp.plexmediaserver.108192

[running] com.skype.skype.111072

[running] com.sonyericsson.Sony-Ericsson-Bridge-Helper.149792

[running] com.spotify.client.112032

[running] com.stuffit.MagicMenu.153312

[running] com.taoeffect.Espionage3.426592

[running] com.twitter.TweetDeck.116512

[running] com.yazsoft.PlaybackMenu.159072

[running] com.yazsoft.PlaybackServer.153952

[running] jp.co.canon.ij.CNSSelectorAgent.158432

[loaded] 409 Apple tasks

[running] 230 Apple tasks

Internet Plug-ins: ⓘ

o1dbrowserplugin: 5.41.3.0 - SDK 10.8 (2015-12-14) [Support]

Google Earth Web Plug-in: 7.1 (2015-06-02) [Support]

Default Browser: 601 - SDK 10.11 (2016-01-25)

AdobeExManDetect: AdobeExManDetect 1.1.0.0 - SDK 10.7 (2013-12-13) [Support]

Flip4Mac WMV Plugin: 3.3.7.3 - SDK 10.7 (2016-02-24) [Support]

AdobeAAMDetect: 3.0.0.0 - SDK 10.9 (2015-10-13) [Support]

FlashPlayer-10.6: 19.0.0.226 - SDK 10.6 (2015-10-23) [Support]

AmazonMP3DownloaderPlugin101749: AmazonMP3DownloaderPlugin 1.0.17 - SDK 10.4 (2013-08-24) [Support]

Silverlight: 5.1.41212.0 - SDK 10.6 (2016-01-16) [Support]

QuickTime Plugin: 7.7.3 (2016-01-25)

Flash Player: 19.0.0.226 - SDK 10.6 (2015-10-23) Outdated! Update

googletalkbrowserplugin: 5.41.3.0 - SDK 10.8 (2015-12-11) [Support]

SharePointBrowserPlugin: 14.6.2 - SDK 10.6 (2016-03-27) [Support]

AdobePDFViewer: 10.1.1 (2013-08-22) [Support]

GarminGpsControl: 4.2.0.0 - SDK 10.8 (2014-03-31) [Support]

EPPEX Plugin: 10.0 (2013-09-13) [Support]

JavaAppletPlugin: Java 8 Update 73 build 02 (2016-02-07) Check version

User internet Plug-ins: ⓘ

Folx3Plugin: Unknown

Safari Extensions: ⓘ

Dashlane (2015-09-29)

OpenIE (2013-08-24)

3rd Party Preference Panes: ⓘ

Backblaze Backup (2015-11-07) [Support]

CUDA Preferences (2016-02-03) [Support]

Flash Player (2015-10-15) [Support]

Flip4Mac WMV (2016-02-24) [Support]

FUSE for OS X (OSXFUSE) (2016-01-18) [Support]

Java (2016-02-07) [Support]

Logitech Control Center (2014-12-01) [Support]

Time Machine: ⓘ

Skip System Files: NO

Mobile backups: OFF

Auto backup: YES

Volumes being backed up:

Macintosh HD: Disk size: 1.11 TB Disk used: 382.42 GB

Destinations:

Backup [Local]

Total size: 999.86 GB

Total number of backups: 133

Oldest backup: 28/08/2013, 04:08

Last backup: 06/04/2016, 16:13

Size of backup disk: Too small

Backup size 999.86 GB < (Disk used 382.42 GB X 3)

Top Processes by CPU: ⓘ

47% Spotify Helper(2)

9% Spotify

6% mdworker(16)

5% Google Chrome Helper(26)

4% WindowServer

Top Processes by Memory: ⓘ

2.45 GB Google Chrome Helper(25)

1.37 GB kernel_task

418 MB mdworker(15)

369 MB launcher

295 MB Spotify Helper(2)

Virtual Memory Information: ⓘ

12.00 GB Free RAM

12.00 GB Used RAM (5.64 GB Cached)

0 B Swap Used

Diagnostics Information: ⓘ

Apr 7, 2016, 07:43:50 PM Self test - passed

Apr 6, 2016, 05:29:37 PM ~/Library/Logs/DiagnosticReports/launcher_2016-04-06-172937_[redacted].crash

com.fsecure.sync.BTCloud - /Applications/BT Cloud.app/Contents/MacOS/launcher

Apr 5, 2016, 06:43:40 PM ~/Library/Logs/DiagnosticReports/garcon_2016-04-05-184340_[redacted].crash

com.getdropbox.dropbox.garcon - /Applications/Dropbox.app/Contents/PlugIns/garcon.appex/Contents/MacOS/garcon