It's possible this could be part of the problem and "cleaning" the
contacts to resolve it
isn't cleaning them of dirt, but of wear particles of adjacent
connection points that have allowed
enough connectivity between contact points for irregularities in
lens-camera operation to
arise.
Check out the image and notice the "connections" between points by the
worn off gold.

http://www.pbase.com/andersonrm/image/59300440