I have an LMT 10.5" upper that I bought in about 2003. It has always run like a sewing machine with a standard buffer. I have often run it suppressed with a Gemtech HALO can I bought about the same time. That said it probably has less than 3k rounds on it. I am promiscuous about owning and shooting other guns, and I don't have the training tempo of the cool guys. I doubt the motorcycle officers in question do either.
I also have a complete DD factory Mk18 that I bought in 2020. It runs very smoothly, and I would not hesitate to recommend it. I bought it as a braced pistol, but I think I am going to eFile a Form 1 this weekend to make it an SBR.