Inaccurate GPS readings

[seattlecubsfan]

I've been getting wildly inconsistent GPS results lately when I've been using my Charge 2 to track running and hiking. The same short run, which I know is 1.4 miles, has registered as anywhere between 1.1 and 1.6 miles. A hike that should have been 2.7 miles was 2.42 instead. Another hike that I know is 2.5 miles was tracked at 3.09 miles.  Another run has registered as 2 miles (the actual distance) and 2.3 miles.

I'm using a OnePlus 6 phone running OxygenOS 10.3.2. This is a new-ish problem. The distances seemed very accurate until about 2 months ago.

Thanks for any advice you can give me. 

Michael

[seattlecubsfan]

Another one, and this was especially off: a 3.1 mile run showed up as 2.38 miles on the Fitbit. The weird thing is that the map accurately displays my route, but the mileage shown on the map is way off. Anyone have any ideas?

[seattlecubsfan]

And most recently, a run that MapMyRun shows to be 2.61 miles registered as 2.05 on the Fitbit. I simultaneously used Google Fit to track it, and it registered 2.65 miles.

Does anyone understand how the Fitbit can be so far off? It's my understanding that it's using the phone's GPS, and the map generated by Fitbit and the map generated by Google Fit were virtually identical, except for the intervals. 

[Bandd]

My fitbit records about 10% more distance than actual. I tried another fitbit charge 2 from a friend, it's the same. very inaccurate for distance. Other sensors such as HR are ok.

Only because of this reason last month I changed to Garmin which has a GPS in-built. So far Garmin watch is recording the distance, pace correctly.