Posted by Drew Hause on November 11, 2019, 7:24 am, in reply to "Double firing"
After thousands of shots, the upper edge of the tip of the sear (usually the right) becomes rounded, causing a light trigger pull or doubling. Courtesy of David Williamson
The cure is an expert smith with a small file.
I did once have a double, and found a flake of unburnt powder that somehow found its way between the sear and the notch