I am having a similar problem - mine is taking hundreds of miles to calibrate, slowly but surely. My mph is correct - but the problem I am having is that the street data in the lower left corner is not coming up. The manual says that when 3D hybrid is complete, then it shall be accurate so I'm hoping that's the issue with the street data.
Pioneer, who is now on my speed dial, says to wait til it calibrates then see if there is still an issue with street data.
I had reset the learning status of the 3D hybrid in my N2 and lost street data, and Pionner told me I had a bad unit. I u