I've glanced over this but not seen any IP rating mentioned for this outside electronic device!
So for me I'd say it shouldn't even be a concern if I were cleaning the windows (but if you have some dunder heed working for you then there's every possiblity). Then if they persist I'd ask the question of the IP rating. Think about your wfp control, it should be able to work in the environment it's to be used! If they have fitted an internal device outside then it won't be fit for purpose end of.
If it has the appropriate IP rating then it's not been fitted properly or it's faulty, again end of!
Were you pressure washing the guys fecking house? No you where cleaning the windows and only the fecking windows with a little 12v water pump.