Wendy's Karcher Pressure Washer (she doesn't usually let me use it) wasn't working properly; the Dirt Blaster Lance (her favourite tool) wasn't producing the rotating cone of very high-pressure water that it usually did.
So, I had a look around the Web, and found the following video, which looked like it might provide a solution.
My Mate VINCE
How to REPAIR a Karcher Dirt Blaster
The above video is of a repair of the Dirt Blaster Lance that was provided with a Karcher K2, and Wendy's Karcher is a K4; however, I had faith that the same approach should work;
BUT, it didn't!
Camera 1 = DJI Osmo Action
Camera 2 = DJI Osmo Pocket
Camera 3 = Panasonic Lumix DC-TZ95
Music = Shawl Paul (Norma Rockwell, YouTube Audio Library)