Good day.
I see a potential problem in tcx files which made by Garmin web-interface.
For example.
1. I have an activity. For example: https://connect.garmin.com/modern/activity/1450930593
2. I downloaded TCX file by pressing "Export to TCX".
3. In the activity_1450930593.tcx file i see this information about the last lap of activity:
<Lap StartTime="2016-11-17T15:08:44.000Z">
<TotalTimeSeconds>6.0</TotalTimeSeconds>
<DistanceMeters>20.28</DistanceMeters>
<MaximumSpeed>3.947000026702881</MaximumSpeed>
.........
There is 6.0 seconds considered as Total Time.
4. But the last trackpoint of the lap contains this information:
<Trackpoint>
<Time>2016-11-17T15:08:51.000Z</Time>
<DistanceMeters>3958.580078125</DistanceMeters>
.........
</Trackpoint>
5. Difference between 2016-11-17T15:08:51.000Z and 2016-11-17T15:08:44.000Z is 7 seconds, not 6.
I suppose, that TotalTimeSeconds field has been wrong calculated. Maybe accurate timing is in *.fit files, but not in *.tcx files.
It all could be just misunderstanding, but maybe something should be repaired...