com.apple.apfsd.wbc_drain

Sure, as stated in my previous post, with 10.15.4 supplemental update the issue did vanish.

So it would means it is back on 10.15.5 ?!

see my state below on 10.15.4

$ uptime
11:28  up 15 days, 13:07, 11 users, load averages: 0.87 0.99 1.11
$ pmset -g stats
Sleep Count:121
Dark Wake Count:104
User Wake Count:53
$

And regularly I can see that my iMac is slower to wake-up as it is in sleep.

In regards of statistic I'm more at 15% of sleep prevented by wbc_drain

$ pmset -g log | grep wbc_drain | wc -l
     635
$ pmset -g log | grep wbc_drain | grep PrevIdle | wc -l
      98

I hope the problem is not back on 10.15.5, I have not yet upgraded.

Still seeing this issue on iMac 5k 2017 10.15.5 2TB Fusion drive.

$ pmset -g log | grep PrevIdle | grep wbc_drain

2020-05-31 19:20:58 +0100 Assertions          PID 95(UserEventAgent) Summary BackgroundTask "com.apple.apfsd.wbc_drain" 74:18:23  id:0x0xb0000821a [System: PrevIdle DeclUser BGTask kDisp]          

Please try http://launched.zerowidth.com/plists/f69bb400-24be-0138-d827-4dc4cb74aa31

"IODisplayWrangler which prevent my mac to sleep" => this one is your display which is on :). When your display will go off your Msc should suspend.

"Reboot does not get the ...drain process back." => be careful for me it takes several minutes to be rescheduled on reboot.

I have the exact same problem with a do it yourself fusion drive in my MacBook Pro. Everything was fine until I updated to Catalina :-( In some way I am glad to hear that it happens with the original Apple Fusion Drives in iMacs as well.

the python file that I downloaded should have a py extension, right? Then I have to put it in a folder on the computer ... How do I have to complete the launched page to get the plist file? Sorry, I recognize that I am a clumsy but I would be grateful if you could help me ... thanks

I think I understand how to build launched…. I tried but the script did not work, however, because I think I made some errors in filling the form. In particular, the tick should be placed under the heading "RUN AT LOAD" or under the heading "LAUNCH ONLY ONCE"? Please let me know ... I am attaching how I filled out the form ... Tell me if I'm wrong ... Thanks ...

It can be true as people are chosing SSD.

however my iMac is recent and was sold with an Fusion drive.

I will contact Apple Care.

I know they won’t do anything but this a way to tell the problem exists.

may be a class action in US would help but I’m quite sure most owners simply don’t notice this issue.

This does not exist, the class action, in my country.

still happening on 10/15/4 supplemental update '10.15.4 (19E287)'

Also noticed that the UserEventAgent that runs the BackgroundTask come.apple.apfsd.wc_drain has its flag 'Preventing Sleep' set to 'No' while it prevent sleep

P.S. A report have been generated indeed using feedback assistant

I found in the system files, in the launch demons folder, this preference com.apple.apfsd.plist which in my opinion is the cause of the problem: I tried to delete the file but it is not possible, it is protected ... According to you it can be solved the bug if you delete this file?