Yes I have a leisure battery set up, but I'm fairly certain it's wired into the main van battery. This is the new head unit, vw compatible dash housing. Not sure about the can bus adapter, but you could be right. It's got me baffled!Have you a leisure battery setup?
Where did they take the power from?
What radio? If not a VW one, then they may have fitted a can bus assist adapter to generate a ignition signal.
Maybe that's dropping out the ignition signal?