I deleted the left half of this window mesh but part of the deleted portion still shows up but when in object mode (orange outline) and when rendering in Cycles. You can see the issue here. I’m in local mode, too, and have nothing else selected, so this glass pane shouldn’t be from any other object.
In Edit Mode, hit Alt-H to unhide all vertices/lines/faces. Then you can really delete it.
Oh my God, thank you!