>>11881636
The rubber membrane under the d-pad may have split or broken, and that can cause buttons to get stuck or not respond with an even level of tactile force.

I had this happen with my first 8bitdo SN30 Pro when they were still getting away with Super Famicom aesthetics. I contacted them about it at the time (2018 or 2019 I think?) and they shipped me a free replacement part.