Oh, that bug is a bummer...
I added the hearts about an hour before the jam ended, I didn't get to much playtesting. It sounds like the global value for the lives is being read before it's updated to be refilled with a new subject.
After the jam I'll come back and remove the lives system anyways, it will be more like you imagined (in where you raise a "tolerance" bar instead of the lives), and I'll add more subjects to experiment on do minigames with too! Thanks for your feedback!