bluekable
commented
6 years ago 
Same specs as above
Not an issue on my mac? Is it perhaps a local issue?
Edit: Apologies I actually could reproduce this however I had to close the expanded app. When I closed it I was not moved back to desktop but rather the window just went black. If I then viewed Mission Control the thumbnail was black. Was able to remove it by clicking the minimize button on the thumb in Mission Control.
jostrander
OS: macOS High Sierra Issue Descriptions: Mission Control thumbnail for GPMDP stays black when it is fullscreen. Steps to Reproduce: Open GDPMP in fullscreen, go to another desktop/fullscreen app, then view mission control.