I kept WinSCP open on the desktop and after I logged in today the behavior returned in WinSCP.
So you do not even need to minimize WinSCP to reproduce the problem?
Before posting, please read how to report bug or request support effectively.
Bug reports without an attached log file are usually useless.
I kept WinSCP open on the desktop and after I logged in today the behavior returned in WinSCP.
Do you perhaps have different display scaling on the new monitor?
I have another monitor and for some reason the behavior is different after it has gone to sleep.