Hi,
When this last happened to me, there was insufficient space in the area where I was trying to place the two controls. On the preview, all looked fine - but execute, and it lost shape completely.
In my case, the label width plus the attribute width plus the 2nd label width plus the 2nd attribute width exceeded the section width which I had allocated.
As a test, perhaps just widen your form to the maximum and see if the problem persists. Check the width of your columns and the separator sections whether expressed in pixels or %.
You may have a completely different problem, but that was my experience.
Peter