Randomly had a "Wiper Motor Fault" appear - wipers got stuck half way up. It was raining and too unsafe to drive, so ended up on a recovery truck.
After several attempts to fix it, the breakdown technician concluded it needed to be replaced. I've spoken to several other owners who have also experienced this. Apparently the underlying issue is that the tracks within the motor get a bit of rubbish on them and this stops it being able to read the position of the wiper arms.
Interestingly, I also found out that (unlike most wiper systems) the motor on the McLaren goes in reverse on the down-stroke - instead of going backwards with an inverted mechanism that reverses the continuous forward motion of the motor. This reduces the weight (no mechanism) but at the cost of motor complexity as it is now essentially a large stepper-motor which can be controlled precisely in each direction.