Maybe a contracts question?

Sherry Mindel wrote:
The dispute is 10 days after they took our old coach and delivered the new one, they tell us rats ate the wire loom in the old traded in coach and want an additional $12,000 for repairs

From what I can tell, all vehicle disclosure laws in California only apply to those selling to consumers. That makes sense, dealers are expected to be knowledgeable and competent enough to protect their own interests.

They did an inspection, found no issues, and accepted the trade at an agreed value. If rats ate wires a day or 10 later, that's their problem. If their inspection didn't turn up an issue, that's also their problem. Since they did 2 inspections, the unit was in their possession the whole time, and only the latter found an issue, I suspect a court would take that as evidence that the damage occurred after they took possession.

I am not a lawyer. Even if someone who posts here is a lawyer, they're not your lawyer. Take all advice as worth what you paid for it.

It looks like CA law requires dealers to pay the collected fees within 20 days for a new vehicle, and 30 days for a used one. Regardless of what the dealer is currently saying, they may submit the paperwork on time, they may just be using that time to make an idle threat to try and get more money from you.

Myself, I'd first contact the DMV and ask about options if a dealer withholds the title/registration paperwork when you have signed purchase documents and made fully payment. They may have some method of getting clean title and registration in that case. You could also contact the district attorney's office where the dealer is located and explain the situation and ask if they consider that to be extortion or some other form of criminal fraud.

If the DMV or DA can't/won't help, time to get a contract law lawyer.