Since the recent firmware update I've noticed the cooling fan has been coming on a lot. I don't remember ever hearing it before the update to be honest, but lately as I turn the unit off I notice the fan has been on, stopping about 10 seconds after powering down. I seem to remember reading (maybe on hummy.org.uk) that it only spins up if the humax is getting too hot. Anyone else noticed it being on more? Should I be worried?