too many to list

the shutter preview lever can become sticky or hard to operate. this doesn't affect operation of the camera but is annoying and can be very expensive to repair.
the window on the back has a rubber gasket material to keep light out. over time it can become brittle and allow light into camera. simply replace it.

The Leica R7 represents a big improvement over its predecessors and overcame much of the shortcomings of the R4/R5 cameras. The R7 is a manual focus camera that provides for manual metering, area metering (center weighted measuring) and overall metering. This allows the camera to change shutter speeds with different lighting conditions while maintaining aperture setting/s. That isn't new...the R4s has those features too. So, what is new is a Program Function that provides control over both aperature and shutter for perfect exposure in quick action scenarios. In T mode or Shutter priority the camera maintains the shutter speed while adjusting the aperture for varying light situations. All of this can be overridden in Manual mode. And there is an OFF position so that battery life is extended.

Weight and feel of the camera is excellent and there is light available so that the aperture is easily seen while viewing through the eyepiece. An opening or window on the back of the camera allows easy viewing of the film canister in case you've forgotten the film speed or iso setting. Of course there is the automatic DX setting that allows the camera to determine that on its own anyway.