Forgot to update here. Made a post on reddit but for transparency purposes I'll update this post too :)
Have been riding more and more in the watery depths and it looks like I found my limit. At least for now.
Was out riding in my usual stream when I dove above the rails again. This time I kept it under and rode it through. It's a really weird feeling.
Didn't notice any issues on the ride home but I noticed when I turn her off she turned back on a few seconds later. After about 7 attempts I realised this was probably due to my earlier ride, water was inside and I needed to disconnect that battery ASAP.
BMS was dry and had no evidence of corrosion. It's covered in conformal coating so I'll expect corrosion near the connectors if any. Battery itself tested fine with each cell pair measuring within an acceptable tolerance of the others.
Controller side was another story. The controller was soaked, drops of water everywhere. This'll be what was triggering the board to turn back on. I know it doesn't take much, just touching the pins on the large battery connector is enough to trigger the BMS to turn on so the water was doing similar.
After removing the top plate I could see additional water on the reverse side of the PCB
In the bottom of the controller box were puddles, yeah I took it too far clearly. Not quite sure where it all came in mind you but I suspect it was around the threading on the power button and charge connector.
Battery box was mostly dry, there was some water in it still especially around the rear lights.
Condensation had formed on the rear lights, I did hear some hissing as I took the onewheel apart around the battery box so seeing this with 0 damage to the BMS has me suspect the rear light has been damaged.
Rear light connector has corrosion, some of the pins have gone blue.
Same can be said for the other side of the connector, this having a lot more corrosion on it. Need to scrape it all off and check connectivity
After cleaning it up I found one of the via's on the rear light PCB was dead so I bodge wired from the output of the connector round to the corresponding pin on the LED bank (was the red ones)
My board is plagued by broken solder joints. My front LEDs actually stopped working not because the cable broke but the connector had broke a pin loose. While testing the light states with the motor plugged in I noticed the lights flickered between states when turning the wheel. Seemed like one of the motor sensor connections were broke. Having already had to bodge wire the front left footpad sensor a few months back I decided to save myself from this again and just bodge wired every active pin on the motor sensor and footpad sensor connector.
After the wiring work I sealed up my controller and battery box ready to seal it up again with the last of my Badgerwheel kit.
Lots of silicone, who needs an internal gasket when you can just gunk the outside ;)
All re-assembled and everything works again. Bonus points for finally getting my front light back up and running after so many months of it being flickery.
I still believe the Badgerwheel kit is great, my last application was 7 months ago and I feel I didn't do the best of jobs applying it. Will be doing a proper seal job soon so I can continue pushing my luck.
Hope the small diagnostics and teardown is useful to anyone. It wasn't the most amazing of fixes since the board hadn't actually suffered any terminal issues.