Did you check where the cables connect into the battery terminal clamps? Grab that terminal clamp and pull it hard. You might find it comes off or at least moves. Both the terminal clamp and frame connection can be perfect but overall the circuit may be weak due to the cable-to-terminal join.Update - John Deere Technician looked at the problem. Immediately went to the battery. Cables looked good. Battery ok. He removed the negative cable. Both ends were good. Checked the area where negative cable bolted onto the frame. Dark in color. Suspected black paint from factory. Used sandpaper to remove paint and shined up the area. Reinstalled neg. cable. Time will tell. He said if not that, then replace ignition switch with exact jd part number. Reason- 2019 model ignition switch will not fit 2018 wiring harness. Hope this helps.