Google translate:
Good morning,
I'm having a problem with the distance on a marathon, I'm missing 50 meters on Strave and even by making the correction I can't unlock my marathon... Do you know if there is another feature to solve this problem? I don't think I'm the first, unfortunately.
Thanks in advance.
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@Romain ILD,
if the “Correct Distance” feature didn't help, it's unfortunately possible that the course was too short. Sadly, some race organizers refuse to get the race route measured & certified, and as a result, the runners end up disappointed.
You could use some 3rd party tool, such as https://www.fitfiletools.com, if you want to add the missing distance. But it cannot be edited directly in Strava.