Reading this chapter I finally figured out what was broken in a few chapters back.
On page 12 at the bottom, the device that shows how much air is remaining, if you check the edges you can see they are cracked.
That's what Baku cracked when Lalo wasn't looking. And my guess on why he did that is to save air in a way that no one can notice.
In chapter 432 page 15 and the beginning of chapter 433, everybody is surprised that Baku is already out of air. This could be interpreted as Baku consuming more air because his physical condition isn't good, but if he cracked the glass on the air device on purpose, it makes sense for him to be out of air early because he wants to fool everyone to think he is out of air while in truth he still has air in reserve.