Hi Norm and Mf,
Yes it's a pity you had all these needles and primer caps failing Norm , I've mostly used the original caps and plastic needles and not
had many problems besides sometimes needing new plastic needles.
I would've thought if you cut the the brass seat and used a new viton tipped needle there shouldn't be an issue with them.
If I had these problems I'd cut the brass seat or remove the new brass seat and install an old brass seat that has a better taper.
Cheers
Max.