As said in the other thread, the error seems to come from Rclone, whilst (I don’t know why and how) Restic succeeds to write the backup.
To investigate further what’s happening you may use the following commands from the app agent environment, e.g.:
runagent -m loki1 # get a shell
restic-wrapper --help
restic-wrapper --show
restic-wrapper --backup 1 stats latest
rclone-wrapper # prints help
rclone-wrapper 1 lsd REMOTE_PATH # write it exactly as-is
BTW restic-wrapper is useful to clean a stale lock on the remote repository.