Okay I got this issue resolved by trying it on a 3rd device (another Mac, this one running MacOS Mojave, rather than Catalina). Renamed the Enpass folder on my WebDAV server, then resynced from this 3rd device. It worked, no errors, then resynced my other devices (another Mac, an iPhone, and an iPad). None of them had issues syncing. So I guess my question is why did this happen? Why did I have to basically recreate the sync for everyone to work again? And what caused the problem in the first place?