Garmin did have teething pains. Our Mooney M20J had one of the first GNS 430s installed and we were some of the first pilots to fly GPS approaches. I remember flying a GPS approach to Waterbury Oxford when course guidance provided by the GNS 430 just stopped. It was supposed to transition to the FAF but no amount of prodding could get the GNS 430 to establish the final approach course. Fortunately we were practicing in VFR conditions. The hypothesis was that the GNS had trouble with three airspaces that were transited during the approach. We submitted a bug to Garmin and a month or so later an upgrade was issued. The field upgrade process is a major advance pioneered by Garmin and contributed to their success. My guess is the other avionics manufactures never dreamed of upgrading in the field. It was “not a thing”. In this era of OTA upgrades, we forget how novel field upgrades were at the time.