I haven't found a way to crash the latest build, so it looks like you've got it fixed. Nice. I think you've got a wonderful core here, made all the more impressive by the 48 hour time limit. The aesthetic is incredible and I like the little touches you made - the bouncing antenna, and one foot dangling as you slide the grapple on the ceiling look lovely.
Honestly, platformers (and so most metroidvanias) aren't really my thing, so you might not want to take my mechanical feedback too seriously, but I found a lot of the game (as far as I got - just one coin and one key) quite difficult and so at times frustrating.
I think you managed to come up with a lot of interesting mechanics aind interactions surrounding the grapple (I only just started seeing the breakable blocks, and I'm sure there were going to be some neat interactions with the enemies), but it often felt like I didn't have a space to experiment, since failure would mean going back quite a way to the last checkpoint and having to redo a number of difficult challenges.
You can't please everyone and I get that I'm probably not in your target audience - I don't think I've played anything close to a metroidvania beyond maaaaybe Rogue Legacy. But for a player like me (interested more in the mechanical puzzles than the execution), the game might benefit from you watching a novice playtester and getting feedback on where/how/why they get stuck or frustrated.
Overall, I think you've done a great job and I'm interested to see where you take it. :)