Every person in my cycling club that has trouble with their Garmin, has the trouble because they don't really know how to use it, or they continue to do things that upset it. IME Garmins work with only minor issues 98% of the time - every now and then they throw a wobbly but this is usually 1 in 50 rides at the most.
If your Garmin is going wrong 1 in 4 rides, you either have a genuinely faulty device, or it is your fault!