Seeing as how its well withing specs I would not worry about it myself but I understand
The first thing I would look at is Chassis ground and battery grounding spot if that is good I would do a wiggle check on the wiring looking for continuety (maybe not spelled right) changes in the ground wires.
The key switch contacts are always suspect as is the starter switch contacts and the kill switch.
Dont over think it and take your time the answer will come to you when you least expect it.
Jeff