I have contacted Service Support on this error for my Rx65. They have told me that a Reset on SelfCals is not good enough.
This only clears the ROM of the failures and if it shows up again there is defiantly a problem with the radar detector.
SelfCal2 is a problem with one of the bands not calibrating correctly.
The radar detector will try to self calibrate on startup and review the calibration every few mins because of heat generation from the unit causes a shift in Calibration if it can't correct the shift bingo you get the SelfCal2 error.
This is what happened to me. (After a reset)
It would pass the initial testing on boot then a few mins later it would prompt me SelfCal2 Service Required and chirp at me. After it had done it once it will immediately tell you of the SelfCal2 error on boot.
Firmware version is 3.2
Very early model.