I have repaired a couple of GM vacuum wiper motors and what I found in both was the paddle (which is a hard rubber or hard rubber coated steel, I dont recall for sure) was shrunk/dried up. I took a gamble and soaked the paddle in dot 3 brake fluid and softened it up a bit then cleaned the housing good with brake cleaner. Then lube the softened paddle with white lithium grease (sparingly). Both motors worked great when re assembled. I dont know if this is CORRECT rebuild procedure but poor men have poor ways.
