Monitors Recognised but unable to move windows between screens
 

No issues with connecting all monitors in a extended display, but sometimes I'm unable to move windows between monitors.

Problem is intermittent which suggests it's not necessarily the software and more me not fully understanding when windows can/cannot be moved between screens!

I've tried fully maximised windows / moving the dock bar to different screens / launching from Finder window/In-App etc. but cannot work out what does/does not allow windows to be moved between screed.

Using a MacBook Pro and two HP E332 monitors with a UGREEN Revodok Pro