To reproduce:
1. Do some stuff while playing a level (anything that gets recorded in a replay will suffice - so, assign skills, change the release rate, or nuke).
2. Restart the level or backwards timeskip to before this stuff was done.
3. Highlight a lemming.
4. Assign a skill to the highlit lemming via right-clicking the skill panel.
Expected behaviour:
If explicit replay cancel is on, nothing happens (except perhaps that the clicked skill becomes selected).
If explicit replay cancel is off, the skill is assigned to the highlit lemming, the assignment is recorded in the replay, and the replay is interrupted.
Actual behaviour:
Regardless of explicit replay cancel setting, the skill is assigned to the lemming, but the assignment is NOT recorded in the replay, nor is the replay interrupted; also giving rise to a desync.
I have already fixed this in the source code, but Nepster may wish to look over this to ensure I haven't broken anything else that he's done for a reason I wasn't aware of.