I have this problem every time I go flying with SkyDemon:

When I am on the ground with Wifi connected, SkyDemon (version 3.4.4.23 for iPad) downloads and interprets all data successfully and doesn't have any errors.
When I am in the airplane with 3G/4G connection on iPad Air, SkyDemon gives me these error messages:

Corrupt data detected while interpreting downloaded GAFOR information.
Corrupt data detected while interpreting downloaded SIGMET information.
Corrupt data detected while interpreting downloaded TAF/METAR information.



They pop out all the time until I lose the connection which is pretty distracting. What causes these errors and how to get fi them?

I'll have to pay more attention next time I get one of these (which isn't that often).  
In my case it won't have been the mobile network asking me to buy more data - but perhaps the content filtering didn't like me flying near Scunthorpe or the TAF had too much flesh coloured content ;-).
Whatever it is, I think we're both agreeing it's the mobile operator meddling with the data for some purpose or other.