Hassle with Carvin electronics

OK, maybe I am just venting, I don't necessarily have a question but all comments or suggestions are welcome.

So, a few months ago I buy a beautiful Carvin LB70PF (fretless 4-string with piezo) from a guy on Ebay. Great deal, quilted maple top, no wear and tear, just beautiful and about $600 with case. Great deal. Two small problems. The midrange knob barely turns and the treble knob turns all the way around without stopping. Volume crackles a little too. Not just dirty pots, I need a new preamp. I thought I could live with it since once it is set, as long as you don't touch the knobs, it's fine. So I don't bother contacting the seller about it who did NOT mention this problem in the Ebay ad.

So a few months go by. Probably the nicest sounding and playing fretless I've ever had, but I will not deal with the electronics problem any longer. Why not buy a new one from Carvin? The normal preamp without piezo is $100 but they don't sell the one with the piezo. I had to call Carvin and explain my problem and they worked it out so that they could sell me a preamp from the shop (meant for the new ones being put together) but since it has the piezo, $200!

So $200 for this preamp, but now the knob configurations are new. The new Piezo preamps come with three normal knobs and two concentric knobs. My bass has six knobs, none being concentric (two in one). OK, so I'll have one of the holes with a plug, but now I need to buy two concentric knobs that will work with this layout. Hmmm, funny thing, Carvin doesn't seem to sell those either (another call).

I hope this all works, I'm bringing the bass in tomorrow to Mike Lull's shop to have him do it all (at $70 per hour - around here in Seattle he is more well known as the guitar customizer and fix-it guy than being known for his high-end basses).

I hope there are no more problems with this damn thing after this, it's just been a pain.