In Lightroom (not Classic), my arrow keys (to scroll right/left in the photoroll) have stopped working mid-session. After a restart it was working again, but stopped again, 15-20mins later.

It’s exactly what I described in the question. I’ve been editing 50-ish pictures, scrolling to the next with right-arrow, and back with left-arrow. All of a sudden it just quits working. A restart got it going again, for a number of photos, but then it stopped responding again.