Triumph and 209 Primers
I had similar problems with the 209 Primers in my Triumph. It does not close at all with the Win777 primers or the regular Win Primers, but is OK with the Remington Kleanbore.
A friend of mine just bought the Triumph, similar problem. But with his the Win777 209 primers did close, but very was very tight, the Federal and Regular Winchester 209 primers did not close at all. He settled on using the CCI primers and the TC primers which are ok.
I believe the tolerances in the action are manufactured so tight that any slight deviation in the primer and it just does not close.
I personally like the Rem Kleanbore.