Sometimes, when I attempt to take a picture, the mirror stays up and the shutter does not fire which leaves the film advance locked. I can manually reset the mirror and remove the baseplate to reset the linkage to make it work again but I don't know why its having this problem.
I bought it recently and it has always been like this for me. This problem happens even on m90 and bulb settings and with new batteries. The meter does appear to work properly and the battery check light does light up. I have tried 2 different new batteries.
Usually, this problem happens on the first attempted exposure after turning the camera on. If I manually reset everything I am then able to take pictures as much as I want until I turn off the camera for a period of time.
Fortunately, there is a camera repair shop here so I brought it in for a CLA. The tech checked it over and said the previous owner had oiled the shutter which was at least part of the problem. Should be good as new in a few days.