Of course you can cancel any contract that has not been completed.
But there are costs and steps and process associated with the cancellation, that you agreed to when you signed the California Assoc. of Realtors contract.
Did you agree to Mediation, arbitration, do you have a lawyer, do you know RE lawyers charge
more than Divorce lawyers, do you know that the chance to collect is Zero, as there
is an option to file for Bankruptcy for the seller.
However, in the short-term and generally speaking, if your agent wrote a contact incorrectly and then you signed it - you are technically culpable for putting your signature to paper before carefully reading it. If this contract was then accepted and you are now looking to make changes or cancel, it is totally going to depend on what changes you want made or why you want to cancel and whether or not contingencies have been removed.
I would first have the discussion with your agent, then his or her broker. They should come up with a strategy to help you out if that is what you want. Good luck!