Actually the sensors are Hall-effect sensors.
Those plastic covers on your passerelle are non-existent on ours. The big problem is that the water gets to the top of the rotational actuator where the “seam” is between the stationary part and the rotating part. In our case after replacement of the actuator I put an stainless disc on top of the actuator and put a huge load of lanolite grease between the actuator and disc. I also drilled some drain holes in the frame that screws on top of the actuator to avoid standing water and to make sure it drains away from the actuator.