GUI not responding after losing window focus @Win10

Hey,
I just installed OpenPHT 1.7.1 for the first time on my Surface 4 Pro.
But beginning with the initial start up it lags up to a minute if I Alt+Tab to the desktop (to link the account in plex.tv/pin). The same behaviour occurs when I let it run in window mode and it loses focus.

The window says ‘Not responding’. It takes up to a minute until it is useable again.

If I just stay in the window or at least dont click on the window again when doing something else, everything seems to work fine (even video playback). But since that prevents me from doing anything else, its not really usable this way.

There isn’t any weird CPU or RAM usage as well.

According to the log, it seems to have problems with my second PMS which is not in the same LAN currently.
It always mentions the XBOX controller and not being able to cache and focus as well.

Could someone please provide me with a hint, whats going on here?

I didnt have those problems with the Win Plex App and Plex Media Player on this machine or OpenPHT on my QNAP NAS.