I’ve been using the rclone backend for a while, for Google Drive (started using restic because I wanted to backup to Google Drive) and when I first started using it was via REST server and never had any problems. Once they made the rclone backend I switched and never had any problems. I do know about the Error: 403 and it was harmless in my case. But other than that, I hanven’t had any issues and I do backup, check, forget and prune via rclone backend. This was my “issue”.
What I do also know is that Team Drives are tricky with rclone. Maybe the problem is using restic for a Team Drive. I tried to make a rclone configuration once for the “Computers” section without success. I don’t know how does rclone works with Team Drives but with regular user Drive works.