Sync does not work for groups, only for users

[stvoigt]

If I am setting "remoteuser"-config (in the remote wiki) to a valid groupname (e.g. admin), I am getting a "transport error - HTTP status 403" when selecting the sync-profile. If I am setting the "remoteuser"-config to a valid username, everything works fine.

[AzureCloudMonk]

I am getting "Synchronization...The synchronization process has been initiated. Check the progress below." followed by the error: "Failed to fetch remote time. transport error - HTTP status 418".

I am using a valid admin username. I could not get it to work whatsoever all using @admin group. At least with a valid admin username it would list the files to sync, but then fails to sync them. I am using the latest version -- DokuWiki Release 2018-04-22b "Greebo" on both the local Dokuwiki on a Stick and on the remote hosted at my ISP.