a while back i bought a CA m15 carbine with a PPA 100 spring,tm ver.2 switch assembly, that was re-shimmed and lubed by the previous owner.
Impossible to tell without looking at it dude.
HeadOnTactical.com
I have the same issue. I used a hicap and it only fed every other bbs...
it was the bbs... took it in to aex today and it worked perfect with a different brand of bbs