Black screen after playing for a certain period of time

Hi all, my game turns to black screen after a certain period of playing but when I minimize to desktop, it appears normal except for the game. However, the alt buttons will appear when I hold alt but the screen remains black. The gameplay is still active too as I can hear the sound when I move the bus and open/close the doors. Any advice?

Try looking here: https://omnibussimulator.forumieren.com/t2017-black-screen-issue in the "Problems" forum.

Thank you for your help