[Andy]

This is how I believe the interference is created. The lifters are tapped with a tap. The threads are the same all the way to the bottom. The adjusting screw is threaded with the same set up from end to end. The interference come from the screw being necked down and then compressed to locally fail the screw causing the threads to to be slightly out of phase. I have not had any luck trying to compress loose screws to tighten them up. I have had good results by just exchanging screws in lifters.