Hi, new here, so here goes…

I recently purchased a Škoda Octavia Mk3 vRS Combi, and mostly, all seemed ok. 

However, the dash display is now showing an intermittent 'No GPS Reception' notification, which causes the number of satellites to drop in/out, and although it's showing long/lat, sat nav is not working correctly. (Strangely, this began a couple days after having the car serviced). 

I've tried the infotainment system reset but to no avail.

The maps aren’t up to date, and I initially thought the issue might be related to that. But from what I’ve read, it’s more likely the ’Shark Fin’ is faulty, as they can suffer from water ingress. I’m looking into buying a replacement, but wanted to ask for further diagnosis advice before purchasing. (any removal/installation pointers would also be appreciated)

Also, I want to update the maps, and have looked on the portal, but can only see MIB2 update. So I’m unsure what the correct update is. The car currently has the Amundsen MIB1 head unit, that has the cd player and two SD Card slots, linked to the 6” screen. (I’m considering my options upgrading the (Bolero?) Infotainment system too but will create another post). 

The original Škoda SD card is in slot no’ 1. And from what I know, this will facilitate the update. But it states on the portal, ‘Delete all data on the SD card’. Is that correct? And I assume 'or format the card', is related to a non Škoda SD card?

I appreciate this topic may have been covered before, but I’m not the most tech savvy, so any clarification or advice would be greatly appreciated.

Regards

p.s. the car does not have a USB input, only the 'media in' port which I believe needs an adapter to use?

Edit:
Unable to edit the initial post but wanted to change the txt to the following:
'I want to update the maps, so have looked on the portal, and can see the ECE 2020/2021 update, is that the correct one?
I can only see MIB2 Amundsen, MIB2 Columbus, MIB3 update manual info.

The car currently has the (Bolero?) Amundsen MIB1 head unit, that has the cd player and two SD Card slots, linked to the 6” screen. (I’m considering my options upgrading the Infotainment system/ head unit too but will create another post). 

Edited 14 minutes ago14 min by Shkodal