Did for some reason the tiller get wet? Remove it and check for corrosion. Second is the tiller cable has a potential to crack and or break wiring. Ohm out the harness from pivot point to tiller connection. 4 wires.
Any green on the tiller e-tac card it must be replaced.
Earlier models were prone to have the lithium battery go dead on the tiller card also. Needs to be at least 3.0 volts. You can replace that battery with a 2016 lithium button battery. Remove the top and bottom flaps to the button battery carefully. Then rough up the surface with emery cloth. Soldier them back on to the new battery. May have to download new software.... But Try it first if you have to replace the battery. That card is expensive and for 10$ you can replace that battery yourself.