Hi,
there are only three components for the wiper, the stalk, the control module ("J31 Automatic intermittent wash/wipe relay") and the wiper motor itself.
If the wiring is OK and you have tried changing the control module and stalk then I would suspect the motor itself.
The motor has an internal set of electrical tracks with follow the movement of the spindle. They are responsible for keeping the motor powered if the arm is not at the rest position when you switch off so that the arm automatically goes back to the bottom. They are also responsible for braking the motor when the arm has reached the bottom when the wipers are off. If the breaking function is inoperative, although the power has been removed, there is normally enough momentum left in the geared motor to continue and move the arm past the rest position and then start the way up again. This then re-engages the motor power and the wipers effectively never stop.
This all happens inside the wiper motor casing. If this is the case you would need the replace the wiper motor or repair it. It may not be fixable as the internals might have worn or broken.
regards
Andrew