I have had my 705 for about 6 months. I just had to return my cadence sensor because it stopped working. Annoying - Garmin was responsive and told me how to return. It was their discretion as to whether they repair or replace which I was kind of unhappy with. After owning for 6 months and paying $600 it should have been "we'll send you a new sensor"! So I don't know what they did but its been 2 weeks and I still don't have it back so it leads me to believe they repaired. I've been told it shipped. The GPS can still calculate avg speed and distance so the only thing I am missing is my cadence number.

I've never had the data problems your experiencing. I say contact Garmin right away! I did it all through email.