Demo desyncing caused by bouncing lost souls

In Vanilla Doom, lost souls were originally intended to bounce off of floors & ceilings when they hit them, but due to a coding error, the bouncing test was preformed after the lost souls's momentum was set to 0. Doom 95 and Final Doom fixed this bug, causing many Doom 2 v1.9 demos to go out of sync.

Source
http://prboom.sourceforge.net/mbf-bugs.html