I know you got a new 722, but the high-pitched/buzzing sound was probably the fan going bad, which is really no different than an 80mm fan in a computer when it is about to die. My 722 was being problematic and was from 2011 and was the 2nd one. They seem to last 4 to 6 years before something goes tits-up. I now have a Hopper 3 and I'm pleased with it, for the most-part except for OTA.