Problem with Steam Link (mouse won't move outside of invisible window)

[~ayjay~]

I tried out Steam Link for the first time with my iPad recently and everything worked fine. When tried to play a game over Steam Link today I stumbled into an issue though which makes basically every game unplayable over Steam Link.

When I start a game over Steam Link in the Big Picture mode, there is an "invisible box" on my screen which is smaller than my actual desktop screen. My mouse pointer is not able to move outside of this are but the Big Picture mode and the games are displayed in full screen on my desktop, so I am not able to reach certain buttons there.

On my iPad, the pointer seems to work normally but does not react when i try to click on something which is "outside the boundary" on my desktop. It's as if the games gets desplayed with the deskop resolution but my mouse pointer is only allowed to move in the iPad resolution.

I already tried:
- restarting Steam on Desktop
- restarting Steam Link on my iPad
- restarting my PC
- deinstalling and reinstalling Steam Link on my iPad and reconnecting it with my PC

Is this some sort of bug or maybe a weird setting issue? Could it be that I accendentally screwed up my settings and if yes, is there a way to fix this?