Mobs not taking the right amount of damage

Hey all! I just started a PaperMC server which was ported over from a Realm. I am completely new to this so I’m sorry about not knowing things.

We’re having an extremely strange issue where mobs simply won’t take the right amount of melee damage. If an unarmored zombie is hit with an enchanted diamond sword that claims to do 10 damage, it takes 10+ hits to kill it (each hit does about 2 damage, he starts with 20 health).

However, this problem is only existent with nonplayer entities. If I am hit with that same sword, I take a full 10 damage (unarmored). This problem persists between all melee weapons, fists included.

It gets weirder. If you were to shoot the same zombie with a bow, it takes the right amount of damage! It only takes ~2 shots from an enchanted bow to kill a zombie.

This has persisted beyond server reboots and across naturally spawned/spawned in mobs (spider, zombie, skeletons, etc.). I am at a complete loss as to what could be causing this. We’re on MC 1.14.4 and Paper #209 (just updated to test it again, we were 24 versions behind, but the problem persists)

Any help at all would be much appreciated!