If anyone is wondering if I managed to get the bug fixed with my fingerprint sensor not working; Short answer: I didn’t. The long answer is, that I opened a request with the seller because of said fingerprint sensor issue. Then I sent the phone (Nothing phone 2a) back to the seller and they checked everything on it. Turns out there was a manufacturing issue where the sensor was just faulty from the get go. So I got a brand new and sealed Nothing phone 2a sent by the seller at no cost of mine. Not even the sending back of the phone I had to pay for. Now since yesterday I’m using the new phone with absolutely no issues. Updated it and all and the sensor keeps working great.
Shout out to digitec.ch for handling this the way they did.
TL;DR The sensor was broken before it left the factory. Nobody to blame here.