Edge 530 wrong climbing/elevation recorded in poor weather

Hi All,

I did a few rides in wet (the norm in England during winter) and foggy conditions.

When saving the activity and reviewing the data recorded by my Garmin Edge I can see that the overall amount of climbing in the activity is significantly lower than expected.

If I get Strava to recalculate the elevation data, I sometimes get more than 1000m EXTRA elevation somehow missed by the garmin (e.g. recorded 1300m+, elevation from Strava is 2300m+).

Is this normal?

Is there an issue with the barometric altimeter of my unit?

I use a rubber cover to "protect" my Edge unit, can that have anything to do with it?

Cheers

Valerio