Garmin edge 800 randomnly changing data fields

AT the beginning of a ride, after I have set my training page for no apparent reason the unit highlites a randomn data field in blue, and then attempts to edit it.  I can get back to the training page by hitting the back button.  Sometimes it randomnly changes the data field from one selection (distance) to another (time to go...).   I am not touching the unit and the physical jarring of the unit does not cause any changes.

This goes a away after about an hour of riding and does not retrun.

Other than that the unit records accurately.

Any ideas!