SFTP with only restic to Hetzner works perfectly fine here in two cases I’m the admin at. One thing that has come up in this forum a few times is that the hardware of the machine being backed up has problems (example) and it only comes up because of restic’s checksums. It happened to me personally once too and it’s scary because we don’t usually notice on consumer hardware and file systems.
Personal note: I find working with large data sets in the cloud always somewhat challenging. If you can, make a local backup and then periodically rsync that to the cloud (3-2-1 backup). Then regularily check the cloud backup with --read-data-subset as @rawtaz recommended. In my experience it’s much faster to do so from a Hetzner VM but my DSL lines are usually extremely slow.
Oh yes and forget chatty… he’s full of b/s.