First time I tried to thread my adapter into a Flow Ti, it was not an easy assembly and it felt gravelly. I think the 3d printing & machining process leaves small debris inside that needs to get cleaned out /burned off while shooting.
That said, mine wasn't a fine thread hub mount, it was the acme style qd thread. I just forced it on and off a few times to clean it out. I would try to remove it and get some solvent and a toothbrush and try to make sure you don't have any junk in the threads. Could also get some thread lube for first assembly to see if that helps.