my ex-wife's cats clawed the gasket
That would have been my wife's ex-cats, followed by my ex-wife's ex-cats! Mine would sleep anywhere warm - top of the amplifier, laptop. Caused thousands in damage. The cat was nearly as bad.
Thanks for the information on your turntable. It does not have an insulated platter, which eliminates that as a potential problem. However, the mats you are using do seem to be insulators. Have you tried a conductive mat? The silk belt could act like a Van der Graff generator but both ends are grounded, so no to that idea.
I think a huge part of your problem could be the synthetic carpet. Have you tried an anti-static spray treatment, designed to reduce static shocks and dust buildup?
I decided not to pay extra for Holbo's dust cover (the transport costs were prohibitive) and I bought some velvet cloth to cover it when not in use.

