The video goes into some detail about the history and significance of the two Latin words "subsitit in" found in Lumen gentium 8.
Surprisingly, how those two words were suggested in the first place is not mentioned.
One story I heard claims that it was a Protestant observer who told one of the periti at Vat.II that the Latin word est could be replaced with subsistit in with great benefit for ecumenical relations. The peritus passed this message on to his bishop and then it moved on up the chain to the liberals who had commandeered the whole shebang, and found its way somewhat quietly into an early edition of LG8. The point being that it is an idea that sprang from a heretical point of view and therefore represents a corruption from the start.