I have an RNS MFD2 in my mk5 and a while ago my battery died so I got it replaced. Since then my head unit doesn't turn on with the ignition if it's been sat for abit. If I have the engine off for 5 minutes e.g. to go in a corner shop, when I start back up the head unit turns on fine. It turns OFF perfectly fine when I turn the car off and take the key out. Don't really know what the problem is, any ideas?