I have been experiencing this bug too, here is how it happens for me:
1. Switch to Sage
2. Use Eukrasian Diagnosis on Self.
3. At this point, the currently equipped SGE weapon model will duplicate and one copy will be behind my character. Certain animations move these models relative to the character but I have not been able to determine exactly what causes what movement.

4. Sheathing the weapon and jumping will teleport the duplicated set of weapons on my character's feet.

Unsheathing and jumping moves them back to where they were.
5. Switching to other jobs and using certain abilities will remove the duplicate Sage weapon models, but instead display another object that is supposed to become hidden after a certain point. These are: Quill from certain SMN animations, harp from BRD, card from AST, and the rabbit for NIN.


Getting one of these models to be "stuck" will remove the last one.
Similarly, certain models from gold saucer minigames can get stuck on my character's body in the same way.




I hope the images display correctly