First, I glad to hear you have one of the best detectors that has come along in the last decade or two. I have two CoRe devices and I will NOT part with either of them. My oldest, 46, son switched over two years ago to the CoRe and parted with his competitor's brand detector. I have several good friends who have also made the Nokta/Makro switch and have a CoRe in their arsenal as well.
Second, to the Tracking switch. When you say the switch works sometimes but not all the time, are you referring to it physically not functioning, or do you mean when activated the auto-tracking circuitry isn't functioning?
Third, the search coils. Unless you have damaged the coils, such as dropping them or banging them around very hard up against rocks or stone structures, then it isn't very likely your coils have gone 'out-of-spec' so to speak. Search coils do not need tom be 'calibrated' to a detector that features Manual Ground Balance, Automated Ground Balance or Auto-Tracking Ground balance, and your CoRe provides all three GB functions.
With some brands and models through the years we have seen the term 'calibrated' used periodically. The most often noted case is with the Tesoro brand, and the word 'calibrated' really refers to adjusting the internal Ground Balance trimmer on their factory preset models. It isn't really 'calibrating' the search coil, but 'calibrating' or setting the GB trimmer so the detector will be functional with one or more search coils. This isn't necessary with a manually GB'ed model as the operator adjusts, or 'calibrates' the Ground balance manually.
With the CoRe, and other Nokta and Makro models, they provide multiple ways for the GB to be achieved.
Therefore, you only have a real concern about the Tracking switch or circuitry that performs the GB adjustment. That only requires the control housing to be sent out for Nokta service.
Monte
PS: Mend well and I hope you enjoy some good times afield this year with your CoRe.
