In addition to all of the above I've found that some Sony remotes use a
spiral wound wire for the poslitive contact. This can be indented
slightly if the remote is dropped. A penknife point inserted at the
center of the spiral will pull the spiral flat or slightly convex. This
will improve the contact.
BTW the old nailpolish remover was acetone which will damage most
plastics. Haven't tested the newer ones.
Richard