1991, 300SL Windshield Wiper Stopping

The windshield wiper occasionally stops during operations. I'm not talking about the intermittent position but when running at low or mid speed. The stopping can occur when the blade is located in any position of its travel
arc, including stopping directly in the line of vision. Leaving the switch remain in the on position, the blade will resume operating "normally" until the next episode. I had the motor greased at the last service but this has not help. Has anyone experienced this problem or can explain what needs to be fixed?
Thanks John

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.