Hi,
My (currently working but who knows...) solution is to create a task (.cmd file) that is executed at each logon (using the Task Scheduler) and that contains these simple lines :
@ECHO OFF
powercfg -requestsoverride PROCESS "MoUsoCoreWorker.exe" SYSTEM
To make things easier and cleaner, this .cmd file can be converted to an .exe file using the Bat to Exe Converter utility (https://www.majorgeeks.com/files/details/bat_to_exe_converter.html). This will allow to launch the command transparently.
Anyway, this is an irritating bug because no one can say when MoUsoCoreWorker.exe will re-appear and post a new request. It's obviously related to recently installed or pending Windows updates but I can't find any pattern. MoUsoCoreWorker.exe is launched each time you check Windows Update in the system settings but it stay there afterwards (not necessarily posting a no-sleep request).
So, Helloooooooooo Microsooooooooft!, time to wake up and fix this.