High Pressure Hose Blew Off The Water Outlet
The high pressure hose was not fully inserted into the water outlet, causing the threaded collar to not be completely screwed on to the water inlet threads.
The high pressure hose needs to be pushed into the water outlet about 1/4 of an inch. The threaded collar will line up to the threads on the water outlet. If they are having trouble inserting the metal end of the high pressure hose into the water outlet, have them coat the o-ring with a small amount of petroleum jelly and try again.