What is the reason that my GPS for bike has lost satellite reception?

I have been using Garmin for about 6 years now. I currently have the GPS 276C. The first unit was flawless for about 4 years then I had the antenna connector go bad. I sent it in thinking they would replace the connector nope replaced. Now that seemed like a good deal to me since I had 3 years of usage and now I have a new unit. Well the new unit had issues from the beginning, the biggest thing was loosing the satellite signal. Most of the time I had to power off/on to get it back. It was not due to hills this was just out in the open. Then it started doing other strange things like never getting a signal, sometimes not even powering up. I sent it back and they replaced it for no charge. The unit I have now is flawless again. I think that they are not really meant to deal with the motorcycle vibration. IMHO Garmin is still the best & their customer service is excellent. Thank you