Inventor of "Y Y" to quit
This seems to affect more demos than that. For instance, 1427uv01.lmp now desyncs (see this post).
I hope that myk has not taken offence that his some demos have ceased to work (they should not work) in PrBoom :)
Indeed, one would expect desyncs with any vanilla demos recorded with Prboom or Prboom-plus where the player has used a key to switch directly to the SSG. I don't know if any regular recorders have that as part of their set-up, and don't have time to test many demos right now.
Edit: I doubt there are very many though - I presume most recorders test their own demos, and at the very least any in demopacks will have been tested, so we'd probably have spotted if anyone regularly recorded demos with this problem.
Two ways to solve this occur to me:
* Make it so this fix is for recording only (so you can't now record a demo with Prboom-plus that desyncs with Doom2.exe for this reason), but not for playback (so any such demos recorded with older versions will still play back OK).
* Add in a command-line switch to enable the direct switch to SSG, so that demos specifically affected can be made to play back. This would be consistent with the solution for the old desyncs resulting from the monsters_avoid_hazards bug.