The issue does not appear to be due to the multiselect integration. The actual _generateCellRowOutline function is called well before initialization of multiselect. The multiselect just loads where the object is located, which originally is in the wrong place as it does not get moved by refreshEditorPos.
It appears that in 7.3 all of this code has been replaced, so I will use my workaround (overriding refreshEditorPos) for now until I get to that version and see if the issue still exists.
Thanks