First off...that's just about the laziest review I've ever read.
On topic, I've bought TSC parts for a WA-GBBR and had fitting issue. The through hole for the sear was undersized and needed to be reamed out. Not much, but enough to set it up on a drill press.
I've had to mod lots of different parts from lots of different manufacuters....just a fact of life when mixing and matching brands. Better that something be oversized than undersized.