Jenniren,
Whenyou washyour car, look at the small vericalpanel which is covered when the tail gate is closed. It is at the end of the roof panel.
I recently cleaned my car which had not ben done for several weeks. This area was covered i a geen mould. It is dificult to get at. It took me over an hour to get it all off
A large bottle brush or similar is useful as you ahev to get behind the two hinges. You may fibnd it difficuklt to direct the pressure washer onto it.
You would also get water inside the car.
Good luckand ope it is in show room condition when you have finished.