Traction battery readout fluctuations with new 12V battery

This is my first post in years.

My 2010 Prius is throwing a hybrid battery fault code P0A80 about every other time I drive. Simultaneously the NAV display state of charge meter drops instantly from five or six bars to two bars. The car drives chuggy with state of charge display stuck at two bars, with apparently no charging process. I have to "clear battery fault codes" with the Dr Prius app and turn car OFF/ON which restores normal driving and charging operation for the rest of my trip. The fault codes cycle will happen about every other drive, especially after leaving the car overnight.

Of course I checked the newer 12 volt agm auxiliary battery which load tested good, even replaced it with a brand new borrowed 12 volt battery. Battery voltage and charging check okay with Dr Prius.

The traction battery is a recently reconditioned unit with about 6 months and 30k miles on it. This problem just started last two weeks. Dr Prius shows battery module Delta V's and internal resistance numbers within normal tolerance. New bus bars were installed in the traction battery.

The car now has 445,000 miles, running great averaging 45+ mpg with the original inverter/converter. I did the head gasket job myself 150,000 miles ago, I think the was my last inverter coolant replacement.

Can anyone please suggest what might be the GHOST IN MY MACHINE ? and a check/test procedure to verify that?

Thank you.