I crafted a Zombie Charm and kept it in my inventory. As intended, it keeps zombies from attacking me. However, when I attack a Zombie, there is a high chance that my game crashes. It doesn’t seem 100% consistent, however. This happens both with sword strikes and with Thaumcraft bolt magic.
I’ve been playing FTB Ultimate Reloaded for a while now without any crashes, so I am confident that it is specifically the Zombie Charm that is causing this crash.
Edit: I’ve noticed that attacking Thaumcraft’s Angry Zombies does not have the same effect. I believe it crashes 100% of the time when the target is a vanilla Zombie.
E2: A Skeleton shot a Zombie while trying to shoot at me, and there was no crash. The Zombie attacked the Skeleton and killed it, then remained docile towards me. Seemed potentially relevant to me.