Originally Posted by DiabloScott

That's certainly a lot. What were the actual values that are 1000 feet apart? And is this as reported on your Garmins or what Strava reported based on Garmin data?

If the actual elevation values at any particular point agree, then it's the way your devices are summing up the totals, and not a measurement error. Strava talks about this in their "smoothing" function.