I've been having trouble lately w/ my rope lower knot spinning.....So, I figure we need to tie on a new loop......Done. Didn't fix it, so we decided that the serving was bad.....It was, new serving time. Done. STILL spinning.......What the??? What else is there? Could I have a thin spot in the string or something??

Are your knots opposite one another? Im not sure that it really makes much of a differance. I always tie mine on the same side and havent every had a problem with it. could be your string is twisting during release and the momentum is spining the loop if your peep and loop arent pointed directly away from the riser at rest. I dunno.