GPS distance

Did you do this test on a precisely measured Course? Which watch was correct?

Yes it is marked out via parkrun route its very strange 

Ianujc80! said:

around 50 meters out over the mile

Ianujc80! said:

seems to be longer every time 

Would you be more precise?

All watches have a margin of error so you cannot expect exact matching. Fifty metres over a mile is really neither here nor there.

Let's just say it is very much out from the other 150 times I have ran the same route before the latest update 

Let's just say that 50m out over 1600m (~1mile) is well below the 5% margin of error for a commercial wrist-worn GPS watch. Do you run precisely the same track each time? Are the satellites in precisely the same position each time?

FWIW I run a parkrun course with markers every one km. The course was measured wth a calibrated wheel to 5.04km (all parkruns should be wheeled slightly long) yet depending on the day, the tree cover, the season, the path I take, I get anywhere between 4.95 and 5.05.

So you did one single run with a bad measurement? There can be numerous reasons for that (signal disturbing GPS, few visible satellites...)

I cannot confirm that it is a madder of the software-version. When running to the gym I mostly run the same course and start/stop at exactly the same spots. The 4,6km course has challenges (valley, dense woods, corners, a tunnel, houses) and the reproducibility of my F5+ is mostly within +/- 10m, sometimes +/-20m - also with 13.0. My Fenix 3 measured the same distance with a slightly higher variance and my Fenix 1 measured around 50m more. Last weekend I did a 13km run with my son, his Garmin Venu measured 100m more. We did a counterclock lap and he mostly ran on my right side - so this seems reasonable within a normal range of error.

I disagree on that - I do a cycle route regularly, it is a hilly 4.84 miles and generally my Fenix 5 Plus reports that distance. I don't think a 500 meter (1/2 kilometer) margin of error on a 10 mile route is what most people would consider acceptable, which is what you imply with fifty meters over a mile being neither here nor there.

My long weekend runs are also very consistant and I'm running 15+ miles on a Sunday.

I personally find my Fenix 5 Plus to be very consistent with known and marked distance. I often run with a Polar V800 on my other wrist, and they generally agree with no more than 0.01 of a mile discrepancy even over long distances.

IMHO 50 meters out per mile is not normal behaviour - cummulatively that is a massive error over the miles! - I've never observed that level of inaccuracy with Fitbit Surge, Amazfit Stratos, Polar V800 and multiple Garmin watches and certainly not with the F5 Plus.

It's definitely changed since the update by more than I would expect I have tried all the GPS types I have power cycled the watch and see how I get on 

Obviously you already know the reason and you do not want to give more information, so be happy that you are faster than your friends now!