I strongly suspect a loose sabot. Crushed Ribs are a great solution for a tight barrel and TC's do have a reputation for tight barrels. However, something is not right.

Are you swabbing between shots?

How much loading pressure do you have? You should have to give it a good push on a clean barrel.

Finally, clean that Pyro well. It shoots fine but is very corrosive and must be meticulously cleaned.