Yeah, Stephen King did.Jordan T wrote:....has anyone else had this problem with their car?

But not with a Triumph and on a truly epic scale:

Self parking switch will probably be stiff as a result of the grease that's designed to keep it dry hardening. If water gets in, they tend to fail altogether in which case the wipers will stop where they are when you switch them off, but if the contacts in the park switch are stiff toward the other end of the sliding contact's travel, then they'll give you the problem you've found.
It's a rectangular plastic box, a couple of Inch or so in length, that simply clips to the wiper motor. Gently slide it out, equally gently remove the two green wires, one with a trace, that are attached to it and soak the whole thing in cooking oil or similar overnight. Then rinse through with contact spray such as Servisol S10 or Halfords' own which is pretty good, apply a little spray grease to the contacts, refit to the motor. Simple as that.