Hi,
I deleted my GC file and imported again my original garmin fit file.
All is ok.
This error is surely a network issue with the server that is connected with the recalculation of elevation data.
I had by myself enable the automatic fix elevation data at import
I disable it
I confirm that was a bad idea, prefer to fix elevation data manually only when is is necessary.
I've seen also the following :
original garmin fit file had no GPS errors at import.
After fix elevation data, GC indicated GPS errors (around 2000).
So ,i think that if elevation data are not very important, it is better not to fix elevation data.
Bernard