My Columbus satnav on my 2010 Superb estate also started to fail, intermittently at first and then completely. It shows 0/X satellites (press Navigation and then Current Position to see this) and soon drifted off the correct position and eventually reverted to a location in Germany.
I have now fixed this problem! It is the shark fin corroding inside. Water gets under the seal as the rubber ages and then into the electronic components. At first it seemed to dry out and the system would work again, but after months it packed up completely. Once removed I could see the screws all rusted inside.
The only solution I found is to replace the shark fin. This is easy and takes less than an hour. Once I had done this the satnav worked immediately.
Order a genuine new part (part no. is on underside of the fin). I paid £74 from Skoda in Sheffield, including delivery - shop around. It comes with a new seal. To change the whole fin you only need to remove the trim on the rear offside pillar (the rear driver side). This pulls off from the top edge (don't lose the metal clips). Then pull down the corner of the roof lining - this is held by velcro. You will see the nut on the under side of the shark fin and two cables going to the right, close to the back edge of the roof. These have connectors clipped to the roof. They are difficult to see without a mirror. Unclip these (they have a securing clip which need to be lifted). Then undo the nut to the fin. Help may be required to hold the fin down. The nut may not come completely off - it has an anti-theft device - a small flap of metal on the nut. Once the nut is turning freely pull the fin up from the outside (may have to pull quite hard). The nut will fall off. Lift off the fin, pulling the short cables and connectors through the square hole in the roof.
Clean the roof around the fin base and fit the new fin by reversing the procedure. Don't forget to reconnect the cables correctly - they are colour coded. When pushing back the roof lining make sure the velcro connects properly and the rear door rubber seal fits over the roof lining. The plastic trim on the rear pillar just pushes on, but if the metal clips remained in the metal pillar when removing the trim, they will have to be pulled out and fitted back into the plastic lining first. Again - check the read door seal is fitted over the plastic trim.
It should all now work perfectly.
