Mate I had the same prob just after fitting the 285's and carrier spacer, it didnt start staight away but raised its head on a trip north to cairns a couple of weeks later and after stopping a few times to get access to the fridge. I recond its the doors from the extra weight of the 285 on the main door pulling the top of the door away slightly and thus not fully locking then rattling.

Most carrier spacers are adjstable vertically, so try lifting the spare higher on the mount to reduce the amount of pull down on the door.

One more thing, Make sure you close the doors firmly to ensure its locked at all points. Worked for me.