Issues with bumpers, x/y/a/b buttons

Tentatively opened my Xbox Elite 2 as it’s outside of warranty so I’m unlikely to get much out of MS at this point.

I have little to no response from both bumpers, and spotty response from my A button, so I’m opening it to see if there’s any obvious issues that I can solve.

As soon as I opened it I found a loose screw stuck to one of the paddle magnets, but no obvious hole for it. I think it’s a T5 – it’s very small. I’m not sure if it’s something that got left behind from the manufacturer or if there’s a job it’s supposed to be doing.

The bumpers look like they’re depressing fine when I press them with the front casing removed, so I’m not sure what the issue is.

Any advice would be very much appreciated.