Had problems last week on 2 occasions while on holiday when I encountered a "road closed" I carried on driving and then took what I thought we be a turn in the right direction and expected the sat nav to re -route me , but case one coming out of Dawlish trying to get back to newton abbot area it took me up narrow lanes steep hills with no room for 2 vehicles and then if anything it was trying to make me drive towards Exeter!!

2nd case coming out of Paignton main car park again following route suggested "road closed" kept driving in right direction next thing I'm in centre of Torquay in rush hour while navigating to Newton abbot!!!

Its probably me but I'm not confident with this system think I'll be putting Garmin in car as back up.

It's not you. It's very slow to get updated info. Most of the time it will say slow moving traffic in x number of miles but do nothing to suggest an alternative. 

Mine loves narrow lanes as well.

 

Keep your Garmin in the car or use Google maps as a back up.

My Garmin is very good most of the time, but for reason likes to send me off the M20 up Bluebell Hill and then M2/A2 to join M25 at Dartford, rather than staying M20 to Swanley then M25. I just ignore. 

Get version 0480 of firmware and the latest maps on there and see if that makes a difference.