[Couch Coop with 2 Controllers] Cannot use LB/RB to switch to skills/passive tree anymore

Been playing a lot of local couch coop recently, and I've noticed the following bug. When a player is opening their inventory, they are supposed to be able to use the LB/RB-Buttons to switch to the Skills-Tab, the Passive Skill Tree Tab and the Character Tab. This always works at first when starting the game.

However, certain player actions made by one player, can "interrupt" the other players UI and forcefully eject them (talking to a Vendor, opening the Stash, possibly more). Sometimes, after being "interrupted" like this, the player then cannot switch their UI-Tab anymore at all. So when they reopen their inventory, they're stuck and pressing LB/RB just closes the inventory instead of navigating the Tabs. This is a bit inconsistent to reproduce, but once a players UI is in this "bugged" state, it is permanent until you exit to Character Selection and then launch into the game again.

It might have something to do with the Gem-Cutting UI, I'm unsure. I haven't experimented around too much, but just by casually playing with friends this bug occured frequently and multiple times over the course of a few hours.

We were using 2 Wireless XBox Controllers.