The buyer (transferee) can cancel the offer as follows, CIVIL CODE
SECTION 1102.3, in part: "If any disclosure, or any material amendment of any disclosure, required to be made by this article, is delivered after the execution of an offer to purchase, the transferee shall have three days after delivery in person or five days after delivery by deposit in the mail, to terminate his or her offer by delivery of a written notice of termination to the transferor or the transferor's agent."
This right to cancel is also mirrored in the CAR RPA and applies whether or not there are remaining contingencies.
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If your agent doesn't know the answer, talk to their broker.