On my server 'vanish' can only use admin players, so the option is set to:
oxide.grant group admin vanish.allow
... and everything else that goes from vanish permissions (vanish.unlock, vanish.damage, etc...).
So only admin players can use this plugin. The problem is that I moved one player as admin, better say two players and both two players as default players can use the Vanish plugin. So it's about the players that were ex admins on the Rust server.
It's weird the same when I use it command: oxide.show user 765611988809xxxxx
show me that this player is still in the admin and default group (see under):
(15:21:43) | Player 'playername (765611982922xxxxx)' permissions:
skins.use, furnacesplitter.use, discordcalladmin.use, vanish.damage.buildings, vanish.damage, vanish.damage.players, vanish.damage.animals, vanish.allow, vanish.unlock
Player 'playername (765611982922xxxxx)' groups:
default, admin
and when I type the command: removeowner 765611988809xxxxx
in the console I get this answer (see under):
(15:24:27) | User 765611982922xxxxx isn't an owner
I also want to add that on my server all the admins are set up as owners.