Rob,
Well, dang ! That's interesting that you can't see any support rollers that the slide room is carried on. Your slide is different than my Schwintek.
But I know on mine, from the time it was new, the rubber seals made an awful squealing sound. Even when lubed with some Thetford "slide seal lube" that the dealer sold me.
So I tried rubbing baby powder on all the seals, and was shocked at how much quieter it was. From that I concluded the seal noise was not a big deal, other than sounding irritating.
Spraying the rollers under mine also makes it a little quieter.
From your vids it sure sounds like metal on metal.
Hope you find the source of the noise.