Imac 5K High Sierra 10.13.6 Blue Tooth Disconnects when Mac goes to sleep

I have been struggling with this for several weeks, iMac 2017 21.5" 4K. I tried all of the recommended tricks, resetting PRAM & SMC, deleting all Bluetooth devices and re-adding, resetting the Bluetooth module. I even went to the extreme of reformatting, reinstalling the OS, all the apps, and only recovering my files from Time Machine. I believe I have found the answer today, which appears to be the app Android File Transfer, which I rarely use. I killed the task this morning which was starting on login, and have put my Mac to sleep several times through the day with no issue. For now, I've removed it from my Login Options, but will kill it again and potentially delete the app if it causes me more problems. If you have this app installed, you might want to give this a try. I did eventually find an article somewhere online that indicated others had this problem.

Apple menu > System Preferences, then click Bluetooth. Click the Advanced Button, then select "Allow Bluetooth devices to wake this computer."

Is that set?

If it happens again you may have success with resetting the Bluetooth module:

hold the Shift+Alt(option) keys while you click the Bluetoozh icon in the top menu bar:

select "Debug"then select "Reset the Bluetooth module".

This is an almost forgotten (or hidden) built-in trick.

Interesting, thanks.

Excellent, good to hear.