Okay, that's my bad. I should have realized it was that simple. Sorry.
Here's such a file. I left in the scale ruler (isn't there some technical name for that?) and the two objects - but there's a bit more behind it that might help.
This was on the 1st floor plan, which is right near the scale ruler. These two ovals were used as part of the toilet and sink on the 1st floor, but, when I zoomed out, I realized that two more ovals, for the toilet and sink on the 2nd floor, were also behaving the same way and were auto-selected with everything else. Even more, when I clicked the icon for a deselect window and deselected one oval, all four ovals became deselected.
ExtraSelect.dxf