Capt. Joe check which software version it is running there may be an update to take care of that issue. I had some issues with my 27c doing the same thing among some other things and there was an update i uploaded it to a sd card and installed it and no more problems. turn on the unit go to the menu select software version it is running then look on lowrances web site to see if there is a newer software version for that unit. it will also tell you what the updates will fix.....jim