Thanks for playing!
I've also been seeing some feedback that the bone and gear balancing was skewed a bit, so I've adjusted some prices to balance it out a bit more (unfortunately that doesn't affect anyone who's already bought the upgrades, but that's how it goes, I suppose)
As far as the shield goes, do you mean the time bubble ability (the one that you activate with spacebar or the bottom face button)? I can look into that, I didn't really test edge cases during the boss fight, so it might be linked to that.
Thanks for taking the time to play and leaving some feedback!