Just tested... it seems if I connect to the monitor directly the problem
doesn't occur.

Guess the KVM does play a part in this. However, I still need the KVM as I've
four PCs connected to this monitor.

It's not a major issue as switching it back and forth would put the system back
to the correct resolution, and it currently doesn't have any serious impacts.
Just that I'm wondering why this problem is only happening on AMD video cards
and not on nVidia video cards.