I’m no expert, but this sounds like a permissions issue.
Check what permissions your user has on that folder from both connections (local, remote).
My bet is you have a user in your smbconfig that has read permission on a folder that generic users don’t have, and while you can see the folder as a new generic user, you cannot see its contents.
I think this because I have run into similar problems when trying to sync my media to a backup drive. Backup drive was all like “yup, got all the folders. Shame they’re empty! So weird” no compy, there’s 8tb in those folder let’s try again…
As I said In no expert, very possible Im completely off base. Good luck!
Edit: I know you said you triple checked. But for my story, my machine had permission, but my new backup drive did not. So, I’d quadruple check. Like, try temporarily removing all permissions and see if it works. If it does, you know it was permission based.