I have owned and used half a dozen Leicas over the years, I am a big fan. But of the cameras I have owned (Nikon, Canon, Pentax), the Leicas are by far the least reliable. My M4M got a jammed shutter mechanism after dropping from a chair onto a carpeted floor, my earlier M4 had the shutter curtains fail twice. My M3 suffered a shutter curtain failure, my M6 was prone to having the rangefinder knocked out of adjustment (though every M I have owned has required this adjustment at least twice), and the batteries going dead every other week. When out shooting with a Leica, I carry a backup, because two times now I have been stuck without a working camera when whichever Leica I was using broke down on me.
With Canon cameras like the F1, I have had an issue with the shutter not working at 1/1000, with the Pentax 67 I have had problems with shutters not working at all speeds. With Nikon cameras, I have never had any problem of any type. The worst camera I have owned is the Minolta X1. I can't believe Minolta had the nerve to call the X1 a "professional" camera, both of the ones I used worked well for short periods of time, but both are now paperweights.
If you want reliable, get an old Nikon F. If it works when you buy it, it will probably still work when you sell it, even if it is fifty years later.