I know I was one of the early people to do the “dance” but that was back under my old username. Of course I didn’t call it the “Plex Dance” but probably something with at least one 4 letter word in it. 
I don’t recall but think I read it as a tip someone else had posted and maybe even Elan had said to try it as a test or diagnostic or something like that. If I were to guess I’d say it probably came from an employee at some part in time to help figure out an agent issue. But that’s just a guess.
I’m of no help, but I doubt it was me. Surely not the name “Plex Dance” either.
@beckfield might be hard to find with the transfer of forums, don’t know. Personally I’m amazed we still have to do this, but that’s for another thread. 
