The Bug:

Vexes raise right arm to attack when they are left-handed, and holding a weapon in their left hand.

Steps to Reproduce:

1. Summon a left-handed vex that's holding a sword in its main hand by using the command provided below.

   /summon minecraft:vex ~ ~ ~ {LeftHanded:1b,HandItems:[{id:"minecraft:iron_sword",Count:1b}]}

2. Watch the arms of the vex closely as it shrieks/charges toward you.
3. Take note as to whether or not left-handed vexes raise their right hands to attack.

Observed Behavior:

Left-handed vexes raise their right hands.

Expected Behavior:

Left-handed vexes would raise their left hands.