incorrect altitude from DEM

After a bike ride
(see here: http://www.gpsies.com/map.do?fileId=sqtqtighyvwatruj)
I noticed that oruxmaps reported altitude of 1786 meters, the same track recorded from a Garmin or uploaded to GPSies reported instead of 1300 m, why?
my settings gps:
- Accuracy gps fix (100)
- NMEA altitude correction (checked)
- Altitude from DEM (checked)
- Interpolated DEM (checked)
My DEM files are from DEM1 apps (Google Play)

How do I solve the problem?

Thanks!