Sorry to hear you're currently having issues, we'll see if we can get you and your friend back up and running.
Firstly if you can shoot the marker with the eyes off, if the bolt moves slightly I would guess that you have too much grease on the bolt. Wipe it down and see if this helps your issue.
If the bolt doesn't move at all, I would recommend changing the 14x2 NBR70 o-ring on your propshaft and the rear 020 NBR70 o-ring on the can.
Both can be seen on page 9 of the following:
Let me know if that solves your issue and if not we'll go from there