Tactical Solutions 22 upper weak primer strike

[Blue_Fish]

I bought a TacSol upper for my Stag Arms lower from a CGN'r and have tried a few different types of ammo in it. It fails to fire about every 10 or so rounds and on examination of the spent case seems to exhibit a very shallow indentation on the cartridge rim. It has been carefully cleaned and lubricated and the lower is brand new. It has a standard full faced hammer. Any suggestions as to what could be causing this problem or should I start looking for other ammunition? I have been using federal bulk which I have read should run fine as well as CCI stingers.