E39 - Intermittent Failure of Wipers

[Pickled Piper]

Hi can anybody help with this issue?

Every few months the wipers on my 528 will just stop working. They will remain in the parked position but no matter where I position the switch they will not function. On previous occasions I have just stopped the car then keyed off and on the ignition. This appears to reset something and then everything is back to normal. This time round I had to key off and on several times before they came back to life.

Thanks in advance for any help.

pp