I have a Helix 10 SI GPS @ the helm, and a Helix 10 Sonar GPS at the bow.  Both have the current software versions, 1.210.  I use Navionics + US & Canada cards in both, and both cards were updated Aug. 2016.  I have both units set to shade water depth deeper than 20'.  The SI GPS @ the helm works as intended.  The Sonar GPS unit at the bow does not.  The bow unit shades water shallower than 20'.  I have swapped the cards back and forth, no change.  All HB offered was to do a system default.  That did not help either.  Next recourse is to send the unit and mapping card in to HB.  Anyone have a tip or two on what setting to try?
Thanks in advance,
Gregory