My 2016 CX-5 navigation went coocoo and the arrow went off road to wonderland. I kept resetting it and resetting it and that was no use.Reception issue is likely caused by one of the two main causes.
1) interference: other electronics on board/near by.
2) faulty GPS antenna
My two cents.
Thanks for the #2 suggestion above. I thought about replacing the GPS antenna in the dashboard right behind the center speaker but I ended up unplugging (disconnect the connector next to the antenna unit behind the center speaker) the GPS antenna. Then reconnecting it after a minute and the GPS works fine again. Make sure you use a trim removal tool to remove the center speaker over to avoid damaging the cover.
I also replaced the original 2016 nav SD card with another SD card I (HERE map) bought from Amazon for about $70.
I will say if you have similar problem with the navigation that the arrow goes all over the places that is not where you are try what I mentioned above and see if that helps.