It's never a specific action that makes you get the white plug. It's interaction with a severe lagger. I've died from a rpg that came through 4 walls. Then white plug. Then respawn. Then as I get close to him... white plug and I'm dead from a supposed punch. Yet I NEVER saw him get closer than 20 ft away.
This is the way I see white plugs. Seems like extreme lag to one specific player or that player is lag switching.