The OSF you mention is usually called the 5F controller. It's the "brains" of the infotainment system, a computer that lives behind the glove box.
Not seen anyone say it's causing HK problems, it has been known to be the cause of the various bongs and crashes on the Mk8 though.
It's an expensive part, £3500...unless there is a TSB for it they aren't going to even think about touching it. In fact the dealer isn't allowed to do any warranty work without the VW computer authorising them... No guess work or initiative allowed.
