maddoc
... likes film again.
I've used 4x SR44 batteries successfully, although Leica Japan didn't like that and removed them from the camera when I got my M7 checked over one time (a service they offer for free for the M7 and other current production cameras).
... they can become short cut inside the battery compartment and overheat. It happened to me once, I couldn`t touch the batteries, they were that hot and it took only about 10s from inserting battery, switching on, over-heating. (No, the batteries were not inserted in wrong direction ...)