Great bass for Metal, but so noisy! ideas?

A friend of mine has a Traben John Moyer Signature that has gotten noisier (buzzing) than it used to be. She thinks the noise problem started after a drop.

It's got 2 Rockfield MM style humbuckers, a 5 way switch and a Rockfield preamp with VBMT.

I have checked the ground connections to the bridge, the output jack, the pots & the switch with a meter. It all looks good. There are 2 new batteries and those connections look solid.

I noticed that the Rockfield preamp is slightly microphonic. When I tap it, I can hear it through the amp. Is that normal? It doesn't seem right.

The only other thing I can think of is resoldering all the ground connections.