As I said, my views are based on CA law only. Results may vary elsewhere. Unsigned will not admissible to probate. Likewise oral “will.” Of course it’s possible that the will can be contested, but in CA the grounds are statutory: fraud, menace, duress, undue influence. Changed his mind but didn’t revoke the will is not a ground for contest. Nothing in the poster’s fact pattern would suggest any of the CA statutory grounds are present here.
“As I said, my views are based on CA law only.”
Most states have similar laws but CA courts have ruled against unsigned wills.