I can confirm that:
- I can reproduce this bug.
- The bug is triggered when the "start-of-level" save state is loaded. So, hitting instant-restart or loading a replay in-game will trigger it, as will backwards framestepping in the first 10 seconds (game-time) of gameplay; but exiting to the postview then starting the level again won't even if a replay remains in memory, and it won't happen if you load a replay on the preview screen.
- It indeed does not happen for floaters. I have checked very closely for subtle differences, and there is no issue whatsoever with floaters.
- This issue is not reproduced by putting a pre-assigned Glider entrance in the same spot.
- The issue will occur if (this reuqires either ninja reflexes or a slight modification to NL's code to pause-on-start) a glider is assigned on the first frame.
- The shadows will show the "wrong" path (the one that turns around) even in situations where the lemmings will take the "right" path, until the glider is actually pulled out.
Not yet tested:
- Does anything similar happen in the case of a faller who has not yet pulled out their glider, when save states are made? (EDIT: Seems not, but not 100% confirmed yet.)