I've never had it lock on me (Neuro 6.0). I keep CAD in upper right hand window and usually have HR at bottom. It would not link with the HR monitor during the link phase out of sleep a couple of times, but since have learned to manually link by holding down left button when the bottom displays distance. IMHO, very good computer if you don't mind the fluctuation in Altimeter readings (most computers do this due to changes in air pressure during a ride).