Just take a look at this image. I've opened lightroom cc in fullscreen, then alt-tab it and after such moves top panel stuck. I have to exit fullscreen and get back to get rid of it. Same was in classic lightroom for ages.
I am not sure what you are demonstrating with your image. I tested Lightroom CC on Windows 10 and do not seem to have any stuck panels after an [Alt][Tab] operation. Can you provide more detailed information?