This is fixed in 96.2 now.
This changelog item, for anyone wondering: "Fix issue where stamping LIGH at the right moment caused every LIGH to strike at once"
drawing a pixel of LIGH, advancing one frame, and then stamping / pasting it would trigger it due to the usage of negative .tmp2. Negative .tmp2 is not supported, so I reorganized the .tmp2 properties.

Please don't delete bug report text in the future ... if I hadn't seen it in time, we wouldn't have gotten the LIGH changes we did in 96.2. LIGH now looks a bit cooler in my opinion. It's less "realistic" but it was triggering graphical glitches in its old state by lasting for only a single frame.