Garmin problem on last hunt, something to think about.

Circle C. As I think you have already figured out, you need to ALWAYS check the communication status of your dog on the dog screen. We have had the same thing happen to us several times but you can check his communication status and it will tell you if you're getting a false reading.
As far as the antennas, you can get some that will give you more range but nowhere near 5 miles. The mag antenna will get you about 2 miles in the woods..
We still always run quick track collars on the dogs too just insurance.
AND lijke has already been said,always calibrate your compass before every hunt and if your hunt lasts over about 6 hours you will probably have to calibrate it again.
The garmins could definitley use some improvement but they are worth every penny and the little bit of aggrevation. If you get one and learn how to use it you will wonder how you ever hunted without it..