shape position corruption

I have constructed objects out of shapes. Sometimes toggling between Design and interaction mode the positions of shapes get fouled up. Usually resetting the % zoom repositions everything and the modes cooperate again. Tonight it's gotten pretty bad. Not sure if I've just had the app running too long? It did freeze up just now. I just hope it's not a bug that will appear in production.

In this case it's the 2 chairs, they're both all lines. Notice the table has no problems. It's made of just rounded rectangles. I have lines mixed with rectangles on other pages and they behave.