There was a bug in v3.6.20.2 causing improper emulation of v3.6.20.1. Using clustered weapons, skunks, longbows or axes could cause a desync. Now, v3.6.20.1 is properly emulated.
To avoid invoking v3.6.20.2's improper emulation of v3.6.20.1, this version 3.6.20.3, when hosting, will avoid emulating .20.1 if there are players with .20.2 present; in this case it will emulate 3.6.19.19 instead. Note that there is still an exception in which a desync can happen: if you are not the host of a game, and the other people in it have a mixture of .20.1 and .20.2, then during the game the .20.2 players may desync and drop out. If the host is running .20.2 then the whole game could desync.
The instant replay fix in v3.6.20.2 was incomplete, and could cause a crash.