Full Screen playback on external monitor changes resolution when switching apps

Hi Everyone,

I'm running the latest PP on Windows 10 and have in total 3 monitors connected, one of which is my external 4k TV (connected via HDMI). I set up the screen as a PIayback Display in Premiere, which works, but as soon as I leave Premiere and go back to it, the Video isn't full screen anymore, only taking up a third of the screen (meaning, you only see the video in a third of the monitors size, and see the Desktop background of Windows 10).

I don't have this issue with my connected EIZO that I also use as a full Screen Display Monitor.

It doesn't matter which resolution I have set-up on my tv, I get the same result.

"Disable Video output when in the background" doesn't make a difference either.

Does anyone also have this issue, and knows how to solve it?

I have an nVidia 1080ti installed with latest drivers.

Thanks.