First suspect when having an intermittent issue is always cables and connections. I've been plagued with this issue previously. I used Caig Deoxit and sponge tipped Q-tips to scrub the contacts on both the cable and the unit. Then applied some dielectric grease. It's been months now since I had this problem and I fish 4-5 times a week.
Dadof4: Voltage readings all over the place is an issue you will need to address. Check your connections. Voltage should not jump around. A lot of people have had concerns about low voltage. Most of the manuals show the input voltage as being 10-32 vdc. That's a fairly wide range.