Caption for the blind: sometimes when you put your trousers down to pee, a they fold in such a way that there is a large crease blocking the line between your dick and the toilet. Unsuspecting of this you start to pee (this crease is not a regular occurrence), and only end up finding out when it’s too late.
Im not sure your illustration or explanation quite fits but certainly every so often. Maybe averageing once a year. something goes wrong and you end up putting stuff in the laundry. Its to unoften to remember the specifics but something goes off script.