Yesterday while fishing a tour. my 788ci in 26 ft. of water would jump to 120ft.bottom then slowly scroll back up ti 30ft.It would show fish at 28ft. in 26ft. of water.All up dates have been installed.Shuold I send it back to HB or what,could it be transd.VERY PUZZLED and don't know what to do next.Any help appreciated CAPP