After a bit time, the server owners is removed from tab and get ghost!

but if I use /vanish 2x, its fixed.
so I think its a bug

This had been posted several times here. As far as I know, it's a Bukkit glitch and there is nothing the EssentialsX developers can do about it for now.

I am using spigot.

Spigot is CraftBukkit-based.