Possibility 1: Insufficient Point Density
I spent some time trying to figure out a way to coerce Strava into displaying various options for moving time vs elapsed time. It turns out that Strava will override the information embedded in my TCX output files based on criteria that they explain in this help page. That applies to Real-World files from GPS devices with a clear outdoor signal taking a reading every one to three seconds. If you are using the "Add Timestamps to GPS Tracks" tool on a track with infrequent points, or if you are using a trainer activity, you may want to select the checkbox that says "Interpolate Files (add trackpoints)". Selecting this option will make your file much larger, but it will put in a trackpoint for every second. My tool just does linear averaging between points to increase the density - so nothing fancy. If the point density is low, Strava will consider the time between points to be stopped time, and this will mess up your average speed. By putting in more points, my tool can override this quirk of Strava.
- Notice the difference in point density between the top track (blue dots) and lower track (also blue dots). In the upper track, Strava may think you are "stopped" between the points.
Possibility 2: Lack of "Breaks" in the track
Strava uses two ways of determining if you are stopped: They either trust the stopped time in the file, or calculate their own version of stopped time based on their "minimum speed to be considered moving" algorithm. If you upload a GPX file, it is not possible to insert laps or breaks - so Strava will always have to use "minimum speed to be considered moving". In TCX files, you can insert breaks in the files... and in FIT files, you can directly specify start and stops. In my tool, I have added the option to "Ignore Big Gaps" (though technically, the gaps can be small too). The way this feature works is that you specify the size of the gap (in time or in distance), and if a section of track exceeds the value you specify, my tool will insert a start/stop in that region of your export. Since you cannot embed breaks in GPX, this option does not exist for GPX. If you export as TCX, Strava MAY respect these breaks. Strava should definitely respect the breaks if you export as FIT. Note that the FIT export option is only available to active donors.
- Another way to force Strava to display the proper moving time / stopped time / elapsed time on an export from the GOTOES | Strava Tools