I took my XA on a distant trip years ago and at one point I found the rangefinder patch had stopped moving. Couldn't figure out what might have happened -- I'd handled the camera carefully, carried it well-padded, never dropped it, etc.
It didn't stop me taking photographs. Zone focusing the 35mm lens and using reasonably fast film worked well for me. When I got home I took the camera to a good technician (now unfortunately retired) who told me a part of the rangefinder assembly had become dislodged. He was able to fix it, but warned me that he had found the rangefinder on the XA to be delicate. I've been extra cautious since then, and the camera is still working as it should!