mac mini 5,2

Thank you. Will explore this once COVID - 19 locked down has passed here in Canada.

1 - Do you think the Magic Keyboard 2 and Magic Mouse 2 could be playing a part in this? Older Hardware Mid 2011 with newer accessories 2020 not 100% compatible?

2 - if, as you mentioned, a pinched cord etc would not the Bluetooth KB or mouse drop connections from time to time while in use? Have run the machine for hours without dropped KB or mouse connections.

Thank you Both for your help.

Have taken steps - 1 - Rest SMC - no joy, 2 - Rest PRAM 3x - no joy, 3 - Run AHT Extended - no joy, 4 - Boot from USB installer 10.13.6 - wiped SSD and reinstalled with all updates.

During the setup, had to use lighting to USB for both Magic Keyboard 2 and Magic Mouse 2 for macOS 10.13.6 to pair devices. They would not pair otherwise - still no joy. Still getting the bluetooth crash only at start-up.

Looking deeper, have iMac late 2012 running 10.15.4 and checked System Info Bluetooth Software version 7.0.4f6 whereas Mid 2011 Mac mini with HS latest running Bluetooth version 6.0.7F18

Kind of guessing therein is the issue. Yes new keyboard and mouse function 100% of the time but the crash at startup.

I will have to live with.

Followup - have paired circa 2012 ( 2-battery Magic Keyboard & 2-battery Magic Mouse ) to this unit. Still getting the bluetooth crash at startup. So this disproves my original idea that newer keyboard and mouse are source of the issue.

Thinking the pinched wire etc as den.thed mentioned maybe the true source of issue. Will investigate once COVID-19 and local lock down is over.

Thank again to you both for all your help.

Have been working on this and testing various setups. Turn off Bluetooth on computer and turn off each mouse and keyboard, attached usb keyboard and mouse. Then did a restart several times with usb mouse and keyboard attached. Checked Console after each restart without bluetooth turn on and usb mouse and keyboard connected. Still getting the bluetooth crash after each and every reboot.

So, something is very wrong in High Sierra?? The only other thing that might come into play was when I received this Mac mini from my son, he was running El Capitan and so EFI Boot ROM was the original 5.2xx. When I erased and clean installed HS 10.13.6 there was an EFI ROM update to 135.0.0.0.0. Any chance this is the issue?

Am download 10.13.6 Combo as we speak. Will attempt to install over macOS 10.13.6 (17G12034). I do have tested Clone of existing setup just incase things go wrong.

Would love to try Mojave but but got cut off. Equipment too old Mid 2011

Tried HS Combo over existing installation macOS 10.13.6 (17G12034) - will not allow.

Thinking of doing another erase and install macOS 10.13.6 (17G66) >> apply the Combo Update you mentioned and see what else auto-update gives.

Have all the time Retired and COVID-19 lockdown here in Toronto

Actually, the problem started right after I erased the SSD and did a Clean install from Bootable Install HD of High Sierra 10.13.6. Before doing the Erase, my son had El Captain on it. The EFI Boot Rom was version MM51.0080.B00. Once I installed HS 10.13.6 the updates ( Not including the Security 2020-02 ) wanted to update the EFI Boot ROM to 135.0.0.0.0. It was at that exact moment my issue ( Bluetooth crashing ONLY at cold startup but working 100% once totally booted. Never any bluetooth drops etc. I am suspecting either there is a pinched wire as previously suggested or the age of this hardware is borderline time to retire. Have tried to wipe and clean install Sierra 10.12.6 but have issues getting it to install. Even tried removing 1 stick of 4 GB Ram and booting in HS, reseating both stick RAM and still issues.

Kind of given up and will just live with it annoying error message.

As for downgrading the EFI Boot ROM, I do not think it can be done except by Apple if at all.

Have continued working on it matter. Have done Verbose mod and tried to video capture. The best I can see is "Airport_Brcm 4331: : get SSIData():Get Failure: Apple 80211_IOC_SSID : 6 " followed by " Brcm kext failure "

Otherwise, system continues to work fine.

Though of 1 - reinstall HS over existing HS via Cmd + R and hope it sorts itself out? or 2 - downgrade to El Capitan, see how it works and then upgrade back to HS and fingers crossed the problem does not reappear.

Thoughts welcome

Have finally install El Capitan on External USB 3 128 GB SSD. Not as fast as internal but ok. So far (early stages) the 10.11.6 boots up and have not yet seen the Bluetoothd Crash in Console. As mentioned still testing so report back in some time