It is possible that the lifter is turning and the rod is not, if the ball on the pushrod is oblong or damaged and keying to the oil slot in the rocker cup, Adjustable do not have that oil slot to get caught on. I have seen old engines, non adjustable that the pushrod ball has worn into the slot and quit turning, not a good thing but the lifters and cam where fine. Is it possible that the pushrod was turning and then got knocked out of the lifter cup and quit, does not seem likely. Your new rocker is it "new" or used? I also wonder if the ball on your pushrods are maybe a little larger or smaller than they should be and not fitting correctly.