Ah, this definitely could've been the case, since I was doing challenge runs! It was either that or an unexpected interaction. I tried recreating it in the base game mode (using cheats for money to get it & other items to test with) but I didn't have any issues.
It was definitely the base bricks, because I remember seeing health ticking down 1 at a time and going to reread the jackhammer to see if I'd missed something. I realise now that my original report was unhelpful because I forgot to actually document the case it was bugged in </3 Apologies for that!
For more helpful feedback: I've overall been adoring it, you took the Dragonsweeper formula and did a great job of expanding it! The only request I have is some sort of item description on the character select, so that I don't have to load into a run to see what items do.