Warning: Floor sketch is invalid - Revit

Question
Warning: Floor sketch is invalid.

Issue: Revit failed to regenerate the floor geometry upon executing your last action.

Answer
You cannot ignore this warning. You must cancel the action. This error might occur if you have sketched an opening in a floor, and then locked that opening to another element, such as a wall. If you move the wall, the opening moves with it. If the opening should suddenly lose its host (the floor), this error would display. You can edit the floor sketch and then attempt the action again.