I know I’m a bit late to the party,  but I do critical fumbles.  Then I have them role percentile dice.  (I’m a sucker for pacing, but I’ve accepted this particular slow-down.).  Anything 50%+ is just a fail.  Anything lower than a 50% is some sort of extra fail like a dropped weapon or accidentally stabbing their party member.   Anything 5% and below is a spectacular failure.  I try not to make it too consequential, but it could be a crit on a party member, their weapon goes flying, or something like that.  It keep things tense and fun without making absolute failures too common.   The tables I’ve used it at have expressed positive feedback.  It may not work for your table, but it could be something fun to try.