the arrows that got deflected from player shield-blocking effect (sneak) if bounce onto another mobs like iron golems, zombies,...(and maybe neutral mobs) will make that mob attack the player instead of the one that shoot out the arrows (skeletons, pillagers and mobs like that) or maybe after they killed the shooter then they aimed for player (even thought the player doesn't shoot arrows). Also, I don't really know if this is a bug but I can make sure that I searched and nothing looked like this.