[bpodnar]

Just spent the afternoon updating the sat nav on my 2015 SQ5.
Followed the instruction manual and all went well but had a few butt clenching moments when I thought everything was about to go tits up.
Finally, inserted the activator, got the "success" screen but then found that all my UK routes included a visit to Ukraine! Changed my location to the UK, deleted all my favourites and historical destinations and now everything seems to be working OK. I'll have a better look tomorrow.
Many thanks to everyone who contributed to this thread, your work is much appreciated.
I will make a donation to the site.
Russ

I've had a same problem when updating to 2018 maps 6.26.1, gps located me somewhere arround the ecuator on the sea in Gulf of Guinea. If I want to add route then route starts  at south europe in Greece (thats because the map is covering only Europe and first roads start there). So the problem was IMHO because I've deleted old map database and HDD nav partition and then installed new maps. GPS position was OK when no route is added, but immediately goes to south Greece if I add any route. After adding route and driving for 1km GPS position has settled down and was OK. If I reboot MMI then GPS position go nuts again but again fixed after 1-2 days. After that experience I never deleted old database or HDD partition just install new maps over old ones and never had similar problems.

I think deleting your favorite destinations or last added destinations is not a solution because I've deleted all when deleting nav database and partition and that was a trigger for problem with GPS.