P0A80 but all voltages look normal?

As cold as your air temps are, those voltages do not surprise me at all. Sounds like you already found it, but here is the reconditioning process overview that describes the process step by step:
Battery Reconditioning - Hybrid Automotive

 

I found quite a bit more than a few weak modules recently by load testing each of the modules with the load tester from HybridAutomotive. It's easy enough to rig something up but HybridAutomotive made it oh so simple. I initially paired modules by load test results. Ended up swapping out 14 weakest modules to just get it done. Didn't want to play to much whackamole. The code P0A80 erased itself from memory. I initially reshuffled fresh modules I purchased from HybridAutomotive to BSU side for convenience and monitoring as I installed n three waves. Putting original modules at opposite end kept them isolated and I could monitor and remove easier. I used the EngineLink app and watched max and min modules as I drove. I removed weakest and set in fresh modules again pushing remaining oldest modules to opposite end!
It really gets easier after the 3rd time! LOL
I balanced them per @jeff652
The code cleared itself after driving. I did three drive cycles. Since, I've ordered 6 more just to eventually get all 200k old modules out. I'm wondering if I can salvage any of the original modules?