I just observed that the "average cadence" value which is displayed in Garmin Connect is wrong in my case.
The displayed value on the Edge 1000 I used for recording was 80 at the end of my ride and - using the Fit File Repair Tool - I can see that this value is stored in the .fit file as average cadence value.
But uploading this .fit file results in a value of 59 in Garmin Connect.
Mathias