File > Exit but dopus.exe keeps on running the background

After performing a "File > Exit" I noticed that dopus.exe keeps on running in the background.
I do this File>Exit so Opus will not access external USB drives anymore.

Nonetheless I can not 'safely remove' them. ProcessExplorer shows 'dopus.exe' is still accessing those drives.

Usually I need to wait a while in order to successfully do this 'safe-removal', or, alternatively, I simply power off those drives.

This is an ongoing problem for a long time already.

Q: how to have dopus.exe shut down immediately upon File Exit?

(Maybe I should simply ignore "The WD My Book USB Device' device is not removable and cannot be ejected or unplugged." warnings?)

Thanks.

The same thing that's stopping Opus from shutting down is what's stopping you from ejecting your drives. It could be antivirus in the process scanning files, or video codecs that have got stuck, or anything else really. Some Process Monitor logs could reveal what's happening.

Maybe safer, but maybe problematic if other things are going on, is to do a restart of your OS rather shutting off your drives.
You may want to do a drive shut off at an appropriate point during the restart.

Noticed that, one way or the other, my reply has gone. I did reply at the time, but apparently did something wrong. Anyway, I found a free and portable tool named LockHunter that nicely shows what is running and allows unlocking a selected process.
It has been of great help.

It hasn't gone. You posted it to a different thread: Easier way to find out what is locking a folder? - #5 by opw62

Closing handles in other processes is a bad idea, except as a last resort. It can result in data corruption. It would be better to fix whatever is causing the drive to remain locked.

Since it's doing things to removable drives and seems to be something at a low-level that can block a process from exiting, my suspicion is it's related to antivirus. Just a suspicion, though.

The Process Monitor logs Jon suggested could still be useful here. Process Snapshots taken after using File > Exit Directory Opus may also reveal what the shutdown is getting stuck on.