When you hold any item in the offhand when using the Alex (3 wide arm) player model, that item is rendered on the side of the offhand rather than inside it like the main hand.
Related issues
Attachments
Comments

[media]
Dupe of MC-82955

Wow... I searched 15w31c bugs and found nothing like what I reported... I searched Alex model items positioned incorrectly, and didn't find that bug at all. Oh, well. At least I can confirm this bug is real.