signed a quit claim on a Grant deed that is recently found to be invalid, Is the quit claim valid or can it be challanged?

Unmarried couple bought a house in CA 12/17. Couple breaks up, man presents woman with a quit claim form and woman felt pressured to sign the document presented without clear understanding as to what she was signing away in particular the money which she used as down payment for the house (approx $20k). A letter was just received explaining that the Grant Deed was executed with errors and the wrong forms were used making the Deed invalid. the womans signature is required to transfer the title and get her name off the property, Is the quit claim previously signed still valid? Would like to at least get the original investment of $20k, the woman suffered a stroke a few months back and needs the cash.