2011 Multivan crankshaft pulley

My 2011 Multivan T5 crankshaft pulley is getting hot and the serpentine belt is regularly failing/melting. I have had all the pulleys and tensioners connected to the serpentine belt replaced. There is a rattle that occurs when changing down gears that my mechanic says is coming from the DSG. He originally suggested that this rattle is the DSG and is causing the crankshaft pulley to get hot. He told me to get the DSG reconditioned. I have rung the DSG mechanic and he says that the heat cannot possibly be coming from the DSG and I would be wasting my money to get it reconditioned. Can someone please suggest why the crankshaft pulley is getting so hot.