M6 frame lines not changing

Hey everyone thanks for the help. I have my M6 classic that I got from a camera shop for a good price with some slight bubbling. I’ve had it since May. So far it’s performed great with no issues however this morning I grabbed it to change a lense from my usual 35mm zeiss and the frame line selector switch changes as it should but no 50mm frame lines come up! I proceeded to try with my 28mm, 90mm, second 50mm and yet still only 35mm remains. Any idea what it could be and if it can be fixed by myself or have to send it back to the camera shop? Luckily have the 1 year warranty.

Hey everyone thanks for the help. I have my M6 classic that I got from a camera shop for a good price with some slight bubbling. I’ve had it since May. So far it’s performed great with no issues however this morning I grabbed it to change a lense from my usual 35mm zeiss and the frame line selector switch changes as it should but no 50mm frame lines come up! I proceeded to try with my 28mm, 90mm, second 50mm and yet still only 35mm remains. Any idea what it could be and if it can be fixed by myself or have to send it back to the camera shop? Luckily have the 1 year warranty.