Launcher will only let me connect to one specific server

[BritishPaul 0]

I'm having strange issue where no matter which server I try to join I get right up to playing (loading screen always shows correct server) then I get kicked due to "Connection to server lost" and then when I press play again the launcher thinks I'm trying to join a different server (last server played - V ++ namalsk) which obviously doesn't have mods loaded for. Using GEforce so only vanilla launcher available. Does anyone know how to fix this please?