P3030 code after cell replacement and battery reconditioning

My 2005 Prius is throwing a P3030 code. About a year ago, I replaced a bad cell in the battery block and did a battery reconditioning using the Hybrid Automotive kit. Everything has been working well ever since.

However, on my Dr. Prius App, I notice one blade voltage keeps going negative:


Yesterday, after sitting for a few months while I was gone, the car threw a p3030 code when I tried to start it. I cleared the code and it immediately came back. The 12V was reading 12.3V, so I charged that for a bit, restarted the car, and haven't got a code since.

I am guessing I have a loose lead or something like that on the battery harness? I was curious why having the 12V battery really topped off might prevent the car from throwing the code.

 

I will reopen the HV and check all the leads/wires/harnesses. This Prius has lived on the coast its whole life and has had a lot of corrosion. In 2017, I replaced the entire battery wiring harness after finding it totally corroded.

 

I finally got around to hunting for bad wires today. Here's what I found:


So, looks like the diagnosis is we need a new ECU and harness. i replaced both of these components in 2018... 6 years for salvage parts isn't terrible. Anyone have a good source for these other than eBay?