[Help needed] Dead alert slider in my OnePlus 12

Hi everyone!
I’m looking for some advice or guidance on how to fix my OnePlus 12 by myself – maybe someone here has dealt with a similar issue or knows a way to troubleshoot it?

The problem is with the alert slider (on the left side of the phone), which suddenly stopped working. At first, I tried calibrating it in the hidden service menu, but that didn’t help (seemed like the phone doesn't get any data from the sensor). Unfortunately, after sending the phone to the official OnePlus service in Poland (CTDI / Regenersis – they refused warranty repair, claiming “moisture” and “unauthorized interference,” without providing any valid proof of that; they wanted to replace the screen and two cameras with total cost equal to a brand new device to make the slider work again...), a few things changed:

• the phone came back with an older software version,
• the slider calibration option disappeared from the service menu and hasn’t returned even after several software flashes,
• a local repair shop couldn’t fix it either – apparently, the Hall sensor responsible for the slider is located between two layers of the mainboard, making it difficult to access.

I’d like to try repairing it myself, but I need some pointers – does anyone know exactly where the alert slider circuitry is located, how to test or re-enable calibration, or if there’s a way to restore that option in the software?

I’m based in Poland, but I’d really appreciate any help, diagrams, teardown photos, or step-by-step guidance.

Thanks in advance – I really like this phone, and it’s frustrating to lose such a useful feature!