I've got the same problem happening occasionally,

PiP keys for my instances are Ctrl+F1 - Ctrl+F5 and when I switch to another toon sometimes the Ctrl key gets stuck.
It gets stuck on the window you swapped away from, hitting ctrl again in that window will fix it.

(Unsure posting incoming
From what I've heard it has to do something with the way windows is handling the window swapping.
I noticed it sometimes focusses the wrong client aswell (focus from Windows, not the focus var in macros)
But since it always happens when swapping in emergencies I tend to just click through my windows 1 by 1 hitting ctrl and ending on my main window.