I found a trick that lets the player glitch up the current checkpoint. This usually results in the checkpoint starting without any enemies, and sometimes parts of the level may be missing too, allowing going out of bounds. Or you just get softlocked. It all depends on which checkpoint you are when you do the trick.

The bad part is that setup for this trick takes 25+ seconds, so it's not worth it in a speedrun all that often. However, there's at least one pretty decent fight skip in Chapter 1 that is possible now with this new find.

The time save is at 2:43 of this video (also contains instructions on how to do the trick):