On the top is the one that came with the gun, on the bottom is the one from my Deringer.
I swapped back to the original, and removed the trigger shoe. With the pump all the way forward, the sear would trip when the trigger was pulled all the way back, but the hammer would then hang up on the trigger plate on it's way to the valve.
I put the Deringer sear back in, and was then able to adjust the location of the trigger shoe so that it would allow auto-triggering, but still restrict the rearward movement of the trigger. Thanks Gunrunner......