I know that generally, our understanding of historical events improves with time, as relevant documents are released. Have there been any interesting cases where consensus has gone from one thing initially, to another, then back to the original?
I can't think of any situations where historians go from believing A to believing B to believing A again, with the exception perhaps of good hoaxes (e.g., Piltdown Man, which is not really history anyway).
It's more like historians go from believing A to believing B to believing A-prime. On the surface it may seem that consensus has swung back to the original view, but the understanding is deeper and so it's qualitatively different than it was before.
Think of the old saw about a high school student knowing that slavery caused the U.S. Civil War, a college student knowing that economic and philosophical issues caused the Civil War, and a grad student knowing that slavery caused the Civil War. It's not that the grad student has reverted in her knowledge, it's that she's gained a more complete understanding that happens to have the same headline as her earlier beliefs.