The RB button appears to be stuck down

I just bought this Thrustmaster 458 used and it appears that the RB button is registering as being held down, even though the button itself is not engaged and moves normally. This is my first wheel, but I see that the right paddle is a duplicate of the RB button and that seems to be moving fine as well, so I'm not sure where the issue lies.

I'm testing this in GRID and I can see that every other button registers perfectly, but neither the paddle or the back button will register an RB input - no matter how hard I press. And yet when I press the Xbox button to bring up the guide, I get pushed to the rightmost menu as if the RB button is being held down.

I disassembled the base and the wheel itself so I could get inside, but I'm still not seeing any obvious issues. I unplugged the paddle buttons from the board and the issue persists, which makes me think that paddle button is fine. (I also tested the tactile switches for the paddles with a multimeter and they're both working properly.) When I unplug the main cable that connects the base to the wheel, the issue of the button being pushed finally goes away, but then I obviously can't press any buttons on the wheel with it disconnected. That makes me think the problem is in the wheel itself and not in the base.