If you added objects, such as doors or windows, to a wall in the host drawing while you had a Refedit session open for an xref drawing, a copy of the selected wall is added to the xref drawing. This occurs because any objects added during a Refedit session are always added to the xref drawing and not to the host drawing. Because the object you added was anchored to a wall, the wall is also added to the xref drawing.
To correct the drawings, review both the host drawing and the xref drawing for duplicate objects. Remove the duplicates from the incorrect drawing files. Allowing the duplicates to remain can create problems with the cutting of walls around doors, windows, door/window assemblies, and openings. Hidden line and shaded views are also affected.
To avoid creating duplicate objects in xref drawings, do not add or edit objects in the host drawing when a Refedit session is open for an xref drawing. Also, instead of opening a Refedit session, you can open the xref itself, and make edits directly. You can then save the xref drawing, and reload the updated drawing in the host drawing.