Design flaw - used faxon upper/lower - Faxon Firearms .308 9310 Bolt Carrier Complete

Here is my dilemma... Bolt Catch would not engage bolt in a Faxon upper/lower. 8.6 blackout build, and took it to a gunsmith to assemble. The smith told me it's a design flaw, so I basically have an AK. Now, Faxon has a good reputation, and makes excellent barrels. I am happy with all the Faxon parts in the 8.6 build except for their bolt carrier groups. I also have a Faxon lightweight 5.56 bcg sitting in my parts bag. It has a weird (firing pin)>retaining pin. Very stiff to put back in, and it protrudes more than what I normally am used to. No biggie, I will probably throw it in a build once I get the adjustable gas block for it.(recommended) I second guessed myself what if the bolt catch is the problem? So, I took a .308 LMT BCG and threw it in the 8.6 build. The bolt catch engaged the bolt with no problems. Also the Faxon bolt was getting scrape marks from pulling the charging handle. The fitment just wasn't there. Maybe I got a Faxon bcg lemon. Decided to return it, and OpticsPlanet was stellar in their services giving me a store credit. As much as I love LMT, I'm can't afford to toss $600 again for a range toy. Going to give cryptic a try this time. Heard they are pretty good BCG's. Just putting this out there for any new AR-10 builders. AR-10 builds can be very finicky when it comes to compatibility. Hence, I used Faxon on Faxon parts. Geissele trigger because they're my favorite. La Rue gets a close second on triggers. I'll still buy Faxon parts, just not BCG's until they prove me otherwise.