I remember seeing a few discussions on here where adding solder to the disk contacts works so you may have to try searching or maybe someone who did it will chime in. I myself have yet to have to do it, but perhaps another 100K+ games and I'll be facing a similar problem.

Have you tried taking the top rotating disk off and cleaning it as well as cleaning the stationary one with the contact points?

If not, I just use some isopropyl rubbing alcohol and wet a small piece of green kitchen scouring pad and gently rub away on the contacts making sure to get in the small groove the wiper blade created over the years. I'll then use the same rubbing alcohol to clean all the wiper blades and springs on the rotating disk. I've seen some of my blades and springs really gunked up and not moving freely, so gently cleaning and working them by hand to make sure they smoothly slide in and out of the small metal tube they ride in worked for me.

If you do take the disk off to clean just make sure to put it back together making the same contact points that is was when it came off. You can always take a permanent marker and mark the sides of both disks at the same point before taking apart, then after cleaning the disks line those same two marker points back up when you put it together and screw the rotating disk down.