i believe that the minutes that garmin shows (wrongly) as not moving are the minutes, through out your swim that the watch didn't have GPS signal. Strava is able to post process that data and give you a more accurate distance. 

in my case it was about…

I don't agree look the total distance in the GPX file and you will see that it is always more than the watch distance. for example today i run a 11.32km (planed on garmin connect) my watch say 11.17km and the GPX file say 11.57km. It is the watch corrections…

I have another explanation for the unforeseen U turns:
I can only speak for Basecamp here, but perhaps other planning tools behave similarly.
When planning a course, it can happen with Basecamp that the route to the next click is unintentionally (and often…

I know that it is fairly accurate when measuring distance on road on open terrain, with few turns.

But I only care about the distance measurement when running on trails. In fact absolutely all GPS watches struggle with accuracy on tree covered trails…

I have been experimenting with various measurements and situations.  Once in any trees, my Fenix 5X Plus shows consistently short distances.  A 10% difference on a 25 k.  This means I was preparing for another 3 km when the finish line appeared.

Garmin says…

This was one of the features that sold me on this product.  As I tend to have a slow club head swing the distances recorded are coming up 30-40 yards short.  Frustrating 

I have had the same issue for 2 rounds this week, did a reset to my watch before I checked here.  The GPS seems to be working, it tracks the distance from tee shot to next short, it goes into score mode when I step on the green, just the distances are…