I know a lot has been discussed about this problem with the Nav 6. I have a Nav 6 that is probably 2 to 3 years old and has been faultless until earlier this year. My bike had been parked in the garage over the winter and when I went out on my first ride the Nav began ghosting. After a bit of research I discovered that the likely cause was dampness so I put the Nav of a warm radiator for a couple of hours. Hey presto it now works as it should. Worth a try if anyone is having similar problems. I apologise in advance if this has already been mentioned.