Multiple codes intermittent triangle of death

Let me start by saying hello.
You guys have saved me multiple times throughout the years with “fixes”...
I’m hoping you can help save my car. I love my little beastie... and it’s my livelihood as it’s now my main workhorse in my brand new taxi company.

I’m having multiple codes...
let me start at the beginning.

I was driving all was well. Parked the car at my parents 30 mins came out restarted and the MFD flashed Prius Lexus Prius Lexus Prius Lexus, (basically I had a car with “species identity” issues at a rave) flashed white then black. Turned the car off and let it completely power off (until I heard the inverter and then the click several mins later.) Turned it back on, It rebooted to the factory default of puke green and worked ok... as I was driving (about 50 miles later) it started freaking out and having a stroke again (above symptoms) except my abs flashed and it beeped once (like I had pressed a button on the mfd) it repeated this sequence 3 times, then the mfd had another mini stroke, and flashed the red car with the ! And “problem” On it.. then it slammed itself into neutral and the red triangle popped up. The mfd started screaming “put the car in “p” transaxle charging” warning message (like what it does if you open the door while in gear.)
Checked all fluids. All are great. Inverter resivour has little whirlpool in it, pump is great)
Turned off and restarted the car (to limp her home) red triangle still present BUT CAR IS RUNNING AND DRIVING GREAT. 58 ave mpg (according to the mfd), smooth quiet wonderful.
Still no check engine light... just red triangle of death.

Turned her off and closed up shop for the night (a Thursday night), went out the next morning she started up no red triangle... but still flashing Lexus Prius Prius Lexus on the mfd. no more red triangle either.

None of the other issues have reoccurred and she’s parked out front all lonely...
not driving it except to Get the codes read at a hybrid mechanic.

Codes are
c2312, b1200, b1210, b1260, b1262

History of car
213k miles
New hv battery 65k ago (battery is running great, not discharging or recharging in seconds)
New inverter cooler pump in July (30k ago??)
12v tested “like new” at mechanics. (Only 2 years old)

Will also add lately every time I get out of the car it zaps me like a static shock and never thought about this being an issue until the other issues arose.

I live where it’s been in the - degrees for almost a month with intermittent snow and ice. (Like -15 or colder day in day out)
I go everywhere and anywhere In my little car as it’s a taxi and there are some shady areas (this car is a little mountain goat in the snow and ice... best car I’ve ever driven in said conditions)

Mechanic thinks I jarred a connection or there is one full of ice or corrosion as the wiring harness runs under the car, or there is a short somewhere in the system. (That’s why I talked about what feels like a static shock after the car is powered off and I get out)
He says best case scenario it’s a rubbed wire or grounded wire or corroded connection, even possibly the power switch ... or maybe it’s a replacement ecm... which is an expense I don’t know if I can afford that this early in my business.

She’s clean and has never given me a lick of problem (other than the inverter coolant pump and hv battery) in the 3 years (100k miles or so) I’ve owned her and I quite love this car and don’t want to scrap her for parts if it’s economical to fix her.

There is another company in the area with 4 gen 2’s over 410k miles and still running great with minimal maintenance so I know it’s possible. (I went rogue and started my own co after working for and basically running the other Co for 5 years, so I know what has and hasn’t been done to them)

 

I wish that were it (I’ve read about them and not seen any posts matching my issues)... would the malfunctioning mfd cause all the other codes??
Would the mfd also work properly until the car goes into gear then start freaking out?

might it just be soldering pin 59 and 60?? Instead of full replacement??
Want to get her back ASAP as cheap as possible and can take the circuit board out of the mfd and have it resoldered at a cell/pc repair place for 35 bucks. (Like hobbit has suggested in previous threads??)

 

We replaced the mfd. worked for 3 weeks. Back to Prius at a rave and black triangle.
Found a second salvaged mfd and replaced it again (because the first was salvaged, you never know) 1 week later back to the same old tricks (flashing mfd and red triangle, no modules talking)

So.... tore the entire car apart checking for grounds and loose connections (because when it failed the last time I got a shock from the car strong enough that it left a welt)

Found a few loose ground points. Tightened them
Put the car back together
Ice will not fire (it has power but won’t go into ready)
Tore the hybrid battery apart it was corroded quite badly and the fan was partially plugged.

The cells test good individuallly after removing the corrosion

The 12v which has tested good the week of this happening is going to be replaced...

I live in a damp area and this winter was very extreme (-30 for weeks and weeks on end)
Will be hooking up to tech stream once I get the battery reseated and hooked back up.

In the mean time I bought a 2009 with 100k on it as the Prius needs to be the workhorse of my mini fleet, the gas was eating me alive the van gets 15mpg on a GOOD day, downhill with a tail wind. The 05 got 35 before it died... the 09 gets 44-50 mpg.
I drive roughly 3000 miles a week... so you can see the importance of fuel mileage...

Any other ideas on things to check?
And could the corrosion on the hvbattery be the issue with this 2005????