Jaguar XF Dec 2013 wipers fault

[Garddwr]

Hi
Jaguar XF 2.3 l Diesel Dec 2013 has developed a weird wipers fault. In the dry the wipers work fine (though I obviously don't do this- just done briefly to test using the screen wash button). After it rains, and ONLY after it rains, they will start working when switched on, wipe a few times, then stop at any odd position on the screen, and will not park correctly. If I switch the wiper switch off and then on again they will do the same cycle but again stop after a few wipes. They will do this for THREE times only - after this they will only work if I stop the car by turning the ignition off, then re-starting the car engine. It then repeats the three cycles only every time and then I have to re-start yet again.
This happens is switch is set to sensor, low speed, or high speed!
It is infuriating so I would be grateful for any help please. I have Googled with no result but I am sure some expert out there will know exactly what this fault is. Thank you

[Bigvic]

If they work ok in the dry, then it must be a rain sensor fault

[Garddwr]

I will be testing with the hose in the morning 😊👍