Alt-Tab during gaming

Very recently I have been unable to use alt-tab during any gameplay. I have searched around and couldn't find too much information.
I uninstalled recent updated Nvidia driver but problem still there. This happens on all games I play. I switch to windowed mode to get by this but wondered whether anyone else has this problem.

I have this problem only when I launch the game by itself, if I have any window opened, like a browser or an explorer, I can alt+tab.

I have noticed the issue affects games based on whether they use DirectX 11 or 12 or Vulcan.
DX11 games seem to work fine with ALT-Tabbing to the desktop (mostly) regardless of whether there are other open windows, as do Vulcan rendered games, DX12 games seem to be the most difficult to ALT-Tab with, but there is no real consistency between games, it seems to be a case of try it and see for each game.
Maybe altering the games properties such as disabling or enabling full screen optimisations will work, but this seems to make no difference on some games while it seems to allow proper ALT-Tabbing with others.
Also try changing the ALT-Tab properties in Windows settings as the way it works was changed a while back.

Alt tabbing in games has always been marmite, Some games like it, Some games dont some games just dont let you at all. Can also depend on whether you're in fullscreen or exclusive fullscreen