I have a Chime account. It's pretty good except for one untenable problem. They routinely reject paper check deposits via the app, and will not tell me why. I

I have a Chime account. It's pretty good except for one untenable problem. They routinely reject paper check deposits via the app, and will not tell me why. I recently had a U.S. Treasury check rejected by them. And in multiple messages, they refused to say why. Their reply apologized for both the inconvenience and that they couldn't tell me the reason for the rejection. I've never had an in-person/traditional bank refuse to explain their actions before this. The rejection might be acceptable with an explanation. The refusal to explain is unworkable. And the explicit apology about the refusal to provide an explanation actually makes it even more frustrating. The problem with "well I rarely need to deposit paper checks" is that what if I have some other problem? And they just refuse to explain themselves?