This happened to me and a friend too. I about rage-quited.

go taaard:

There is a Covy Mega-Turret on the mid-right of the map. It's shooting at your Cargo Ship.

So basically, yes, there IS some artillery...

That explains so much. I will certainly remember that when I play it again.

Paddy42:LULZ i never have a proble with this mission.

Did you play on Legendary?