Todd is definitely right about how much has changed in their "engine" and how the layperson has little understanding of how it works under the hood. That said, there are some classic "Bethesda bugs" that have managed to hang around for a long time. For example, every one of their games going back to at least Oblivion has shipped with vsync on, and would have weird issues (typically with physics) when it was disable and the framerate went about 60 fps.