Microprocessor Reset - resets the microprocessor only: INFO/BACK
Not sure what you are reading, but a microprocessor reset returns the 4520 to its original factory settings, thereby losing not only the configuration customizations, but also the Audyssey calibration. As noted earlier, restoring from a network configuration save is the quickest way to get the settings and calibration back to what they were.
I have experienced the third issue with my 4520. The first issue is the loss of settings when there is a power interruption. The second issue is the failure of the front panel headphone jack. Yesterday, I started getting an intermittent connection when using the Audyssey mic. It seems to be a mechanical issue with the internal 3.5mm mic jack, perhaps a loose connection on the PCB behind the faceplate. I can wiggle the jack, and the Audyssey setup screen complains that the connection to the mic has been lost. It also lost connection several times during a calibration, causing that set of measurements to be lost.
I discussed the issue with Crutchfield, from whom I purchased the unit back in October. They graciously offered to ship me a new replacement unit, and the new unit will be shipped immediately, allowing me to continue to use the current one for the time being. I mention this because this is an example of good customer service, exceeding my expectations.