Some other random thing, Gedda's air attack can sometime hit with the stun and not the damage, but only if you just barely hit them
One backup later in case you want the save data, I will try to beat the game again.
Almost made it past trumpet fish, but then died and now trumpet fish won't continue, so the bug may have something to do with dying?
Made a video of me playing though just to see if that helps you find the issue.
Edit: After getting past that somehow, I have a few notes on the boss.
The rock on string can be burned again if you die to boss, in which case it falls through the floor. You can also get hit by it.
Pinecone boss hurts you when falling, which is a bit annoying as you would want to stand under the boss to hit them, but it is not that bad. Same with getting hit when the boss gets back up, annoying but easy to deal with after the first time.
The boss's pacing could be better, the first phase goes on for too long compared to the enrage. I personally think having enrage happen somewhat sooner would help with that. Another way would be to split the boss into three phases, without changing anything else.
Secondly is the enrage itself. The boss yells at you and turn red which indicated a phase change, but the yell itself is an attack bringing the rocks down, which as you are paying attention to the boss as it enrages and the screen effects hides the rocks, you don't notice and unless you are already at the edges you can't get away from the laser attack by the time you notice that it is an attack and not just part of the phase transition.