If the OP is prepared to send me the BCM for a few days I'll happily look at the wiper relay in it FOC. Could just be a cracked joint on PCB. Some ABS modules are well known for this type of fault.
Robert G8RPI.
(professional electronics engineer, been repairing and designing electrical and electronic bits on aircraft, cars and other stuff for over 30 years)
I will definitely do this, should we find that everything else is working fine and that it must be a BCM module.
I would also throw you some cash for doing it!
January is perhaps the only time I could go without the car for up to a week.
How long is a comfortable time for you to have it to fix it for?