P0A08 on my 2008 Prius, but 12v looks OK and hybrid batteries are green

I haven't driven my Prius in a few days and got in on a chilly morning, turned it on to warm up, and within 10 minutes started to drive. There were no errors, but as soon as I started to back out, it immediately threw the red triangle and beeped at me, lighting up all the ABS/etc lights.

This past year I have replaced both the inverter pump and coolant control valve (not at the same time, because apparently, I enjoy spreading the suffering).

I've easily driven 5k miles on the new pump and maybe 1k miles on the coolant control valve. I could be making things up or forgetting what it was like last winter, but it seems to take forever for the heater to warm up (not sure if it is related or simply paranoia that I messed things up during the coolant valve replacement despite no related trouble codes).

The only 2 error codes I have are: P0420 (this one confirms the CEL works by keeping it lit), and P0A08.

The 12V battery is reporting 14V (while idling with headlights on) according to Dr Prius.

I couldn't tell if the inverter coolant was getting agitated because the ICE was on, but I just read another P0A08 post where someone recommended pressing the power button twice without my foot on the brake, so I'll try that when I get home to see if my coolant pump went out already. It was OEM, so I'll have to see if there's any chance of a warranty swap (I doubt it for DIY work).

Here's a screenshot that shows the widest difference between cells I could capture, do you notice anything of concern on this, is there something else I should check to better diagnose the issue?
(over 250k miles on original hybrid batteries, and Toyota's website says there's no recalls for my VIN, but I bought used and don't know what recall work they've done in the past)

Thanks for any tips or pointers, really hoping to avoid an inverter swap if I can.