I've replaced two of these already, I think it's when water gets trapped in them from running off the car, then freezes, which loosens the whole sprayer enclosure, resulting in the centre "popping" out. Basically, you just need to turn it back and forth (using a wrench helps too) until it pops out - at this point, you just remove it from the sprayer tube (make sure this doesn't disappear back into the hood enclosure) and snap it back in. Takes 3 minutes, a simple repair - but you do need the new part from the dealer.