Using '/replaceitem' to replace an Armor Stand's offhand item crashes the game. I first discovered this when I attempted to place a Totem in an Armor Stand's offhand, and my game crashed. Any time I load that world, it instantly crashes again.

With further testing, I learned that every item crashes the game when placed in the Armor Stand's offhand (Assuming it can be placed in it's offhand, e.g. Arrow).
Steps to reproduce:

1: Place an Armor Stand.

2: Run This Command: /replaceitem entity @e[type=armor_stand] slot.weapon.offhand 0 (item)

3: Game Instantly Crashes.