Hi /p/

I'm having a weird issue with my camera... I grew up shooting my dads old medium format camera and just love (or used to?) the 1:1 framing, so when i upgraded to digital I set the camera to output as 1:1 which also allowed me to be immediately used to shooting since that's what I learned on.

Fastforward to today, see everyone posting 2:3 or 3:4 ratio pics and laughing at anyone posting 1:1 I decide to get with the times and try it out. Pretty happy with my adaption to framing but noticed this weird defect where the 1:1 part of the sensor looks a bit more underexposed than the rest of the sensor, has anyone experienced this before?

Is there anyway to reset the sensor or something? it's like the area i've been using for the last near decade is worn out while the unused section is fresh as day 1, I do tend to underexpose a bit so never really thought the sensor was degrading until I saw this.

What can I do? it's out of warranty I guess, do I need to buy a new camera or does anyone retrofit new sensors?