I have noticed some issues with the way plex detects keyboard shortcuts when playing media.
If you accidentally hold the spacebar for longer than 1 second, plex will continue toggling pause/play indefinitely, even though you have released the spacebar.
A similar thing happens with “Shift + (arrow key)”. if you hold the keys for just a bit too long, plex will just continue skipping episodes super fast, until you release one of the keys.
I’m using Google Chrome on macOS