Had the same sensor and rear one not working with the rainx Orange stuff like most people here.
I replaced it right after the bmw one was empty because it was just awful the smell. So disgustingly nasty that I couldn't even use it.
And I love the rainx one. So, anyway, she brought it in and they said that it was due to the rainx stuff. They charged her $90 and said its out of warranty because you used a non bmw fluid, so it doesn't cover it. I should've gone myself. That was to diagnose, flush and add the "toxic crap".
Does anyone know where it says "must use bmw windshield fluid"?
Anyway very annoyed!
I won't use that nasty stuff, I have to find another alternative. Maybe other color rainx or similar. It appears it's the Orange one.