I keep finding my PC going into the screensaver while VLC is playing, and I think I've found (at least one) way to repro.
If I watch a video in VLC and let it end, then double-click another video in the Windows Explorer, (go into fullscreen or not), and not interact with the computer, it will go into screensaver after the set screensaver time. If I then pause and then play the video, it seems to grab the wakelock just fine.
I've gotten in the habit of immediately pausing and playing videos after double-clicking them, but I forgot to yesterday and discovered the issue is still occurring.
Has anyone else been encountering this? Can anyone else repro?