My credit union doesn't accept any check deposits without signature endorsement from the recipient. I have a joint savings account with my spouse. They do not accept checks made out to both me and my spouse if only one of us has signed the check. They do not accept checks made out to me if they are unsigned even when my spouse delivers them in person.
Several other money.SE answers make clear that signature endorsement is not necessary, and specifically point to Uniform Commercial Code §3-206. What arguments can I use to persuade my credit union to accept deposits to my account without my signature, at least from my spouse?