Light Primer Strikes with my Model 1917

[Sentryduty]

Wing nut thing to check from left field, try removing the firing pin and rolling it across a sheet of glass. Look for bends and wobble, had an experience once where the pin would fire occasionally, other times the drag of being "forced" back onto centre by the firing pin hole was stealing enough energy to make ignition unreliable.

Cheap and somewhat easy to check.