It seems that the auto intermittent wipe can a problem & quite costly to fix. (Mine has a damaged gel pad between the sensor & the screen.)
The simple fix seems to be to disconnect the connecting plug in the sensor housing which causes them to work as you would expect on regular vehicles.
(There is a clip along the whole bottom of the sensor casing which pulls downwards about 1cm by the tabs at either side. The cover then hinges off upwards to allow access to the connector.)
Hope this may help some of you!