Fitbit Versa not tracking distance correctly

[Ryry77]

I have a problem that I haven’t found on any other threads involving my specific case so I created a new one.

I purchased my Fitbit Versa 3 days ago so I could stop running with my phone in my hand which I always dropped or it died mid-run. Today, I ran a race which is exactly 3.1 miles or a 5k and my time crossing the finish line was 19:45 which is pretty **ahem** good. I stopped my Fitbit as I was crossing the line and the watch’s distance was way off at 2.5 miles and said I was running at an 8:00 pace which is definitely not right speaking how a 19:45 translates to 6:22/mile pace and I was running so much faster than 8:00/mile. 

I have also noticed something involving setting my stride for my Fitbit to make the runs much more accurate as opposed to the auto set it has it at right now. Does this mean I have to constantly change my stride on the app if I want to run at a different pace in order to get accurate results?

The only reason I ask this is because I am a very innacurate runner with runs all the way in the 9:00/mile pace on long-distance and runs in the 6:00-7:00/mile pace on short to medium distance runs which is an extreme variation in stride length. 

[Marrrmaduke]

Normally Fitbit uses average stride lengths across the population (age, gender, height). If you ever measured your stride lengths, you can turn off the automatic setting and input your values. I wouldn't do that though as I noticed Fitbit seems to have issues with it. Also, each time you start run exercise on your watch with GPS tracking, Fitbit will automatically adjust your running stride length. So, I would leave everything set to auto and go for several runs with GPS on. Once Fitbit collects and calculates data, your numbers should get more accurate.

[lyndac54]

I walk the same walk every day my fitbit versa says I've done 10 miles one day and 8 or 4 another I've reported it and apparently it was fixed NOT