In retrospect, this episode might have been doomed from the beginning.
Any episode that came after Peter Capaldi’s classic performance in “The Zygon Inversion” (which I’m still thinking about today) was going to suffer by the mere fact of its juxtaposition. So you can’t fault Doctor Who for choosing such a radically different episode to follow it.
But radically different doesn’t always equate to good. And “Sleep No More” suffers less from the juxtaposition than from one fatal gimmick.