There are two distinct problems that can occur with the Knight on occasions.

1. the primer backs out of the battery cup and sticks in the nose of the bolt. Oddly enough the primer in a shotgun primer measures .209" - the whole in the face of the bolt of a Knight is .176/.177" and with pressure and heat - especially heat. At times the primer will be heated and pushed out of the batter cup and back into the face of the bolt. Snapping the trigger will push the primer back into the battery cup and then it will fall out of the breech when tipped.

2. The primer, actually, the battery cup expands so much it sticks itself in or on the walls of the primer pocket of the breech plug. This one I hate - when it happens. It is sort of like a shell sticking in the chamber of a CF rifle. Usually because of a dirty chamber or shell. Since CF cases are mostly brass we do not see this problem as often because bras expands to the size of the chamber and then quickly cools and contracts and reduces in size so it can be easily extracted... Shot gun primers or battery cups made of aluminum - not so much!

I have found most often but not always - when the primer pocket gets dirty or sticky the aluminum sticks very well to the walls - especially right at the top of the pocket where the aliminum or even a brass battery pocket can grab the inside lip of edge of the pocket.

So out comes the JB's and I end up trying to clean and smooth out the walls of the primer pocket...

AND THEN... as Josmund suggests... Is there any chance the vent liner has eroded to the point that you are experiencing an unusual amount of back pressure? there is always this problem especially with heavier bullets and charges.