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Unreliable GPS with 8 month old 255

Hello all,

Just a quick one, I've been with Garmin for about 3 or 4 years now, second watch is a Forerunner 255 which was purchased last August. All firmware is currently up to date.

Recently I've been noticing more and more drop outs in GPS signal mid-run for no obvious reason. As per the below, running the same route 3 times over 3 weeks it is throwing it out at random points in different places. Whilst training for a half marathon this isn't ideal. 

I know the limitations of GPS in built up urban areas/ near body of water, with interference etc. The watch is set to all bands for highest accuracy. 

Effectively, I ran this route a few times and for a few weeks had no issues (but have on other run routes) and then twice in the space of the last week its thrown me off massively in random places. First up is a run where it recorded accurately through including the right start and end point. 

Then last week it threw me off in the middle of a running track and has my end point over half a mile from home. Today, despite  having full lock before hitting start, the first two and a half miles of the run are in random locations when I ran the same route as the first image. 

Again, this is with a watch on highest accuracy settings, full 15 second reset last week after that bad run, with full lock before starting. There are no tall buildings and the start of the tun is in a normal suburban residential area with no tall building or tree coverage to effect the signal. The middle of the run is in a country park and hence I can't understand it throwing me off into the woods from the running track. 

Has anyone got any suggestions or should I be submitting a warranty claim for a bad watch? The watch has suffered so significant falls or damage that should have affected it. 

Any ideas anyone? 

  • I have noticed that my PC bag is sometimes stopped in security checks on airports because of the reflective bands on the rain cover. So it seems like reflective material can affect radio waves.

  • I've checked the strips on my jacket but they are quite distant from the watch - half way up the forearm. Can't see anything around the cuff that looks suspicious. Think I'll give it another try with the jacket covering the watch and see what difference that makes.

  • I think I solved my problem. What I did was
    1. deleted the RemoteSW folder (was empty)
    2. synced the watch with garmin express

    The last couple of uses the GPS lock was quick and the tracking is accurate.