A concept, container or paragraph drawn with the Convex shape sizes itself: the box hugs whatever it contains, and it offers no resize handles because its size is not the user's to set.

After closing and reopening the diagram, those elements offer resize handles again. From that moment on, touching one of them is enough to turn the automatic sizing off for good - a single click on a handle, without dragging it anywhere, already does it, and the element is saved that way. The box then keeps the size it happened to have and no longer follows its content.

Expected: an element with the Convex shape keeps sizing itself for as long as it has that shape, whichever way the diagram is opened. Automatic sizing should only give way when the element is genuinely resized by hand.