I am delighted with my Grand C-Max - all bar one niggle: the built-in sat-nav. I have used several external fits before (Garmin. Tom-Tom) but this Ford item is not my favourite by any means.

It struggles to find addresses in the UK and is worse in Europe. 

It is inconsistent about road naming/numbering.

It cannot count roundabout exits and often gets it wrong.

Destinations are sometime stated to be on the wrong side of the road, which matters on dual carriageways!

Local mapping is cheap and often not up to date so one way streets pop up unexcpectedly (in Europe mostly). 

The pre-loaded lists of places of interest is hopeless - seems to have no idea what grocery means, has no supermarkets (except oddly Lidl?); food selection for restaurants is absymal (no Spanish or Portugeuse at all!), historic sites turn up all over the place, tourist attractions are for the child in you,... I could go on.

The problem is of course that with a fitted sat-nav there is little option but to persevere. When a Tom-Tom proved equally crap I was able to give it to a friend, lying fulsomely but even so I could hardly ask for anything in return,  and replace with another Garmin.

Any other views?

Is your Sat-Nav up to date? I used to have the same problems as you but in my current 2012 Focus. The maps /software hadn't been updated since 2012 but since buying the newer SD card for 2017 its worked so much better and is proving far more reliable.

EDIT: I can see yours is a 2017 - but worth a shot at seeing which card they installed.

Mines ok but then it's sync3 mapping is not up to date but waiting for a new release but it's ok