2004 645 electronics problems

[x5bimmers]

Please help. Anyone knows the components involved in wiper/washer controls?
The car randomly turns washers and wipers on for years now. The dealer's computer determined that the control switch is the problem right after it happened and they plugged it in. Well - I've replaced the switch - it wasn't it, I've replaced (first unplugged) the rain sensor - it wasn't it either, checked the washer pumps - those are fine. All the functions of control switch (arm on the steering column) work just fine otherwise. It is basically a command to a quick auto wash and wipe = when water runs out it is still wiping, sometimes once, sometimes 20 times... annoying.
Some people say it could be a steering angle sensor, some say that fail/safe module has something to do with it... Bottom line is that people who make this car (BMW) won't release any info and send you to a dealer, who unfortunately don't know much. (Can tell you stories - for another time)
So logic is the only way to find the problem - what is involved in control of this loop? Or anyone knows the specialty shop who knows these cars electronics and is willing to help on the phone (not asking for free!) what to trace? I would appreciate any positive tips anyone can come up with.