Found something strange when i have equiped shield (Mist Stranger skin) any backpiece skin will not show and after swap to rifle it return back. It is pretty odd looking when using Back/Glidder Combo skins.
If not wielded, the character will wear the shield on its back and thus replacing any backpiece you're currently wearing.
At least this is my experience.
Was I able to help you or give you a hint? Click on Helpful and/or Thumbs up, I would appreciate it alot!
When you encounter a bug ingame, at first you should file a ticket via the ingame command /bug, as only this way the devs will know exactly where you were, when the bug happened.