^ Absolutely. There are mistakes that go out the door with every make. It's just a part of reality.
But what I'm trying to point out to
@Keystone19250 is that in this specific case,
his case, although going for a supposedly higher-quality (either or both of build/assembly and/or components) upper should give him better chances that the final mating to his lower will be trouble-free, it doesn't
guaranty such.
Look at this
n of 1 sample of a SOLGW East India upper, via SOTAR's awesome YouTube Channel:
I'm just trying to temper expectations, that's all.

Things can happen, even with top-flight stuff.
And more towards this -
^ I think that this SOTAR comparison of five KAC Sandcuttter BCGs (top-tier) is a very good example of minor variances that can potentially show unique issues when placed into unique final systems.
^ And here's an "autopsy" of one singular example of yet another Sandcutter - was this an escape from QA/QC?
Similarly, here is an
n of 1 of a LMT enhanced bolt (top-tier) ---->
And finally, even more on-point, this is specifically explaining tolerance stacking - again, all the parts used here are considered top-tier:
Pay special attention to what Albrecht is saying. Tolerance stacking is possible, even with excellent components.