JMW9sig mistracking

I have recently accured a VPI SSM JMW9sig with a Grado platimum and love it (it replaced my LP12)
In general it tracks everything complex/loud /dynamic music no problems. BUT on some (3 so far) records its mistracking at the track lead in ie its fine while playing music but on the silence between tracks the arm shakes quite violently left to right and then mistracks.
Unfortunatly the records this happens on I bought after selling my LP12.
Is this purley a pressing issue or something more sinister ?
Sounds like a variation of the famed "Grado dance" or "Grado wobble," although this usualy makes itself known at the lead-in grooves. When I had a Grado on my JMW 10.5, it affected maybe 10 records in my entire collection and I could never get rid of it altogether, although playing with VTF and the damping fluid in my arm helped somewhat. I hope someone else has had better success in coping with this, if indeed my "diagnosis" is accurate. Good luck, Dave
Done a search and yes looks like I suffer from both grado dance and Grado woofer wobble. Nice to see I have all the Grado traits for my money. I would have been unhappy if I only got the Grado dance :)
Oh well it was only ever a temporary cart, on the phone now to a Lyra dealer.
I have a Lyra Dorian on my JMW9 - Scoutmaster. Sound is superb and no tracking issues. I already have the itch to upgrade to the Helikon but must resist.
You can usually eliminate the grado dance on the JMW 9sig by adding the VPI 3 gm headshell weight. I used one with my Sonata and the dance was gone.
You can experiment by taking 3 gm of blue tac and placing it on the headshell, rebalance and give it a whirl.
I think you'll have the problem solved.