Switching App Intermittent Issue

[rodnaph]

Hi - bit of a vague bug report I'm afraid as the issue is intermittent.

My setup is a use ctrl-number (1, 2, 3, etc..) to switch between apps, with each app full-screen, and one desktop with a few other rarely used apps (which i don't have shortcuts for).

The issue is when I switch to an app, sometimes it displays the desktop instead of the intended app, BUT if I type it still seems to go to the app... so it seems to have focus somehow but not be visible. If I switch to another app, and then back to it, it usually displays normally. Does this sound familiar at all?

Interestingly, I also tried Apptivate and this exhibits the exact same behaviour!?!

I'm running 11.2.3 Big Sur, any info you can provide would be helpful, thanks.