Did you find a way out to resolve this issue?
If you are restoring a backup file why not do it with no config?
tabadmin restore --no-config tabserver_bkp-2018-08-07.tsbak
This way you don't bring the auth related setting during the restore. If you need to add Auth back in - do it after the fact in Tab Config.
If this helps please mark it so other's can benefit from it.