Stage 2 boss. Can't seem to use fire wheels the frame after jumping and I have no idea why.
EDIT: This actually isn't the final branch (it enters the boss 1 frame later than optimal) but it doesn't matter since a 1 frame delay is needed to get the boss kill to work (and another 1 frame delay is needed on top of that). I'll just be moving on with a two frame loss to what I can only assume is emulation differences.