I'm having the exact same issue. The retailer sent my PX-S3000 to the distributor when mine was sounding like kybdsammer's video. It came back with traces of lubricant on the top and down the sides of all the black keys. It fixed the problem for about two weeks before several black keys started to make the same clacking noise again.
I sent it back to the retailer a second time, and they told me they now can't find any issue and there's nothing they can do (I suspect they didn't inspect it under the hood, they just played it – possibly in a noisy environment where it was difficult to hear the problem). I even labeled the keys that were problematic for its second repair.
Now I'm not sure what to do.
