I've noticed that fighter damage is bugged. It adds your strength bonus to hit but you get a -# to your damage sources. I received both a -5 to slashing and -1 to thunder damage on one roll using a thunder enchanted longsword as well as a greatsword. it seems like the -# is kinda random as it's not always the same.
Do you have Karmic Dice enabled? That can do weird things.
I'm assuming that to be the most likely cause of this issue, but just to cover bases, do the enemies you're hitting have any damage reduction effects? Magical plate, dragon, Warding Bond, Blade Ward, or Rage?
also shield does not work properly. it works backwards. If you are hit it wont ask if you want to cast it but if you are missed it will ask if you want to cast it.
What are the specific circumstances? Is it happening when +5 AC would be enough to cause an attack roll to miss? It shouldn't proc at all on crits.