Adobe has acknowledged this bug in the official Adobe feedback forum: Lightroom 6: Problem when viewing images and video full screen (F key related). Please add your vote and opinion to that topic to make it more likely Adobe will prioritize a fix.
my screen is freezing when I go into the fullscreen mode. I operating Lightroom on a QHD monitor on my laptop. The fullscreen mode need a lot of time loading the image espacially after using the paintbrush on the foto. The screen shows a loading message and jumps back and forth between full screen and developer mode. Sometimes the program doesn't load the photo even after 1 minute and then I can't leave the full screen mode and I have to close Lightroom completely. I have the newest version installed of lightroom. The fotos have a size of 20MP in RAW. It's not a issue with the performance because when I turn on the taskmanager it shows that the system isn't operating on the highest performance. Otherwise lightroom runs fluently, only the full screen mode is on hacking. So the bug is still there and isn't fixed as the official Adobe feedback forum says.
Need help. Thanks!
Dell XPS 15 9550
Intel Core i7-6700HQ
32GB main memory
Windows 10Pro, version 1709 (64bit)
Nvidia Geforce GTX 960M
Lightroom Classic CC Version 7.0.1.