How does one fix the elevation gain chart to reflect the most accurate gain/loss during a run/bike ride? I've noticed over the last month or so that my elevations reads are ridiculous and does not show ups or downs, just a flat line. The gains reads for example range from 20,000 to 64,000?? Do I need to send my Garmin 910xt back for replacement or is there a way to manual adjust it?
Sounds to me like the barometer in your 910XT has failed. Most Garmin devices with barometric altimeters (but not all) have a way of calibrating the altimeter before you start an activity. But even if you didn't calibrate, you shouldn't see a flat line. I'd get it replaced.
If you're talking about the chart on Garmin Connect, on any activity page under the little picture of the device is an "Elev Corrections" selection with a drop down menu to the right. Click on it and set it to "Enabled", and GC will ignore the elevation as measured by the device and will use a map to set the elevation of your track points, so your profile should look more or less correct again.
Not directly in Garmin Connect. If you are familiar with Javascript coding, you could use the Local Overrides in the DevTools of the browser, and automate the setting, but other than that, no.
