I am running a navionics chip on my console unit & have it linked with bow unit. After being on a while my contour lines wont show up on my bow unit, so I turn it off turn it back on and it works for about an hour and then does the same thing. It will still show the map but not contour lines, but my console unit isn't doing this just the bow unit that is linked. Any ideas on how to fix besides turning it on & off?? Thanks