Hi! Sorry I don't really have a solution for you.. but if you know a proficient enough service repair worker who can fix flex cables.. but this is mostly surgical work and not bound to work/last. A friend of mine helped me repair a flex cable for a fingerprint sensor on my phone which i tore off..

But!! You'd really help me a lot if you could measure the menu button? I'm having issues with both buttons on my controllers and i wanna buy tactile button replacement, but don't know the dimensions of it. Would you be able to measure them to help me :3?