Okay, mea culpa (my wife says hi). Your own recommendations up top seem sensible, though I would replace the white lithium grease with a drop or two of Mobil 1. Yeah, I know Mike used to recommend the grease, but they also recommended Slick 50 for a while and that stuff turns to GOO.
Another recommendation, straight from VPI, is to clean the belt and then boil it (no kidding) for 30 seconds or so before putting it back on the table. I've heard various boiling times; Mike told me 30 seconds.
Frankly, though, the OP reminded me of what a lack of pitch stability sounds like. My SDS appeared to be dead-on, speedwise, winter and summer, as tested with a KAB strobe, but there was still something wrong. It didn't bother others and I tweaked the hell out of the TNT. I've already mentioned what "fixed" the problem for me.
Another recommendation, straight from VPI, is to clean the belt and then boil it (no kidding) for 30 seconds or so before putting it back on the table. I've heard various boiling times; Mike told me 30 seconds.
Frankly, though, the OP reminded me of what a lack of pitch stability sounds like. My SDS appeared to be dead-on, speedwise, winter and summer, as tested with a KAB strobe, but there was still something wrong. It didn't bother others and I tweaked the hell out of the TNT. I've already mentioned what "fixed" the problem for me.