2021 Tesla Model S — brake fluid is old but still looks clean — trying to narrow this down

Charge curves lie if you don't match starting SOC and temp. Match starting SOC and battery temp if you're comparing 2021 Tesla Model S charge sessions. That's where I'd start. I'd want a dollar figure or a measured spec, not 'should be fine.' I'll poke at it this weekend.

Low-voltage gremlins will strand you even with a full pack. Try a second charger before blaming the 2021 Tesla Model S — site sharing and pack temp change the curve a lot. I'd do that before spending real money. Any freeze-frame data saved? I'd rather pay for diagnosis than a second guess-repair.

I'd treat 12V warnings as a no-ignore. On the 2021 Tesla Model S, I'd get the 12V/DC-DC side checked even if the traction pack looks fine. That's where I'd start. On “brake fluid is old but still looks,” that was the fork that mattered for me. Write the result down so the next test isn't a repeat of the last one. Cold start is when I can actually reproduce it.

Low-voltage gremlins will strand you even with a full pack. Try a second charger before blaming the 2021 Tesla Model S — site sharing and pack temp change the curve a lot. Then you'll know the next fork. Happy to compare notes if your setup is different. That's my plan before I call anyone.