Did you record with a new device?
If your recording device has a barometric sensor that is working correctly, you should have these settings in the Actions - Settings menu
My Garmin Fenix 7 has a barometer. I have configured it as follows, and it has improved, but it still does not give the exact altitude that Garmin or Strava show:
Now the altitude in intervals is 35, but it should be 37. The same thing happens in the other activity: intervals shows 399, but it should be 397.
It’s not a big deal, but I don’t know why there’s a difference. There never has been before, and I haven’t changed my watch, although I think there may have been a software update.
Since it is not important, I believe we can close the incident. Having reviewed past activities, I can see that there is sometimes a difference of 1 metre up or down.
If you did already re-analyze, try reprocess. The ‘climbing’ summary field should just copy whatever is written to the FIT field by your device.
If you did not re-analyze/reprocess, the climbing field has been calculated with the Intervals algorithm and can have small differences due to rounding errors and differences in the algorithm.
Complete explanation is here: