I was told to use Marvel Mystery oil in the air mist unit for the shot pin to help it operate smoothly.
May be worth a try for you.
Somewhere in my files I have a service bulletin That George(Machintek)
sent me on how to service the shot pin and transmission
Will take some digging but can find it if it will help you
You can see the shot pin cylinder on the lower right side of the transmission
with the 2 airlines going to it
Never had mine out but does also stick at times