I Have a 598CI HD SI COMBO . Last year it was working fine I remember I was a little above 750 hours on the unit. This year I every time I turn on the unit it resets to stock settings. So every time I turn on the unit I have to go turn off max mode and change the sensitivity. These settings do not save. I noticed last night that my hours have reset, maybe not sure when but I have 70 hours on the unit now. I contacted hummingbird. No help from them I can send the unit in for $350 and they will repair it. I would rather spend that on a new unit. I'm wondering if there is an internal battery. My warranty is long gone so I'm not opposed to opening it up myself if the battery is on a board. Has anyone ever had this happen. I any guidance would be much appreciated.