1) If you create a symbol out of a simple square, (maybe 400mmx400mm) and use that as the symbol for a seating layout, then recheck the measurements, do they seem to be off? (Its looking like something that needs to be submitted, but I wanted to make sure it wasn't related to the symbol.)
2) I think this is occurring because the focus point does not relocate when the boundary of the seating layout is reshaped, so the point that was previously the "center of mass" in the seating layout boundary that the focal point was lined up with is now off to the side in relation to the focus.
I see this as a bit confusing, but i'm not sure if having the focus point move around when reshaping the boundary would be better or worse?