I have a weird lag where when a vanished player logs on, the chat freezes and stops. And if 2 vanished players log close together, either one's minecraft crashes or the server does.
I don't have any server.log errors for VanishNoPacket around this time either.

The only new plugin is our new one we got from someone who makes us plugins. Its a more in depth socialspy that lets us see ALL commands and chats for our HeroChat.

See what happens when you disable that new plugin