Trial Keys in off-hand won't open a Vault while holding an item in main hand

If you right click a vault with a trial key in your off-hand while also holding an item in your main hand, the vault won't open. 

What I expected to happen was...:
The vault should open, since it does when you don't hold anything in your main hand.

What actually happened was...:
The vault stays closed. Main hand plays the animation.

Steps to reproduce:

1. Hold a Trial Key in your off-hand and another item in your main hand (not a Trial Key).
2. Right click a Vault.