Yeah, this is weirdly typical of almost all products. Pretty high dollar ones, stuff from the US, from Norway, everything. Almost nothing is tight, is loctited, and often enough it doesn't even quite fit. Not sure when we all gave up on shit working the first time.
Half the time you complain to a gun parts supplier the answer is that you should have had a Qualified Gunsmith Perform The Installation. Aside from fuck that, find me a qualified gunsmith anymore.
Glad yours worked out to grind them down. Chasing the threads usually works just to spin on a corresponding nut before cutting the screw, then twist it off. I also have some very sharp files (e.g. a sight dovetail file) and as I get older use the magnifying light to line it up and cut the thin bits and burrs off the thread opening to make it work right.