Q: iPhone bluetooth issues with Mazda car

I have an iPhone 5 which I use in my Mazda 5 car to play music through bluetooth. Recently it has started to skip and slip. It seems to be worse when in built up areas. This did not happen before and have had phone and car for over 12 months.

There have been problems that the track would change on the iPhone but the display in the car would freeze and still show the details of a previous song and sometimes the controls would become unresponsive. I have controls on the steering wheel to change volume or move to the next or previous song and sometimes the song would not change.

This was annoying but the current problem with the skipping and slipping is making it almost unusable.

Any ideas?