Solved: Voltage Drop on DC Panel
2016 AI GT
Posting should anyone else have these symptoms.
I was experiencing a 1.4V differential between the DC distribution panel and the batteries. Took me several hours to trace down to a corroded bonding cable connection located under the R.S. cup holder.
A tail-tail sign is a big disparity between the Touchsensor reading versus the Magnum. In my case the Magnum was spot on with battery voltage so through exploration learned that the DC panel's Common relies on the AS installed body bonding cable. You can see below the corrosion that was around the connection. Cleaned things up, added a washer for more surface area and things are good as new.