Ty for playing!
Yeah so the intended use of elements is that enemies each have their own type - Fire, Water, or Nature. Your cards can have no type, or one of those types. Fire beats Nature, Nature beats Water, and Water beats Fire. Cards should deal either double damage along those lines, or half damage in the opposite direction. (No element or same element deals damage with no multiplier).
The real bug is that behind the scenes cards are incorrectly reporting their element to the combat system, so sometimes you're not playing the element you think you are. Whoops.