Web page designer leaves a dragged control overlapping another control

In a web project's page designer, dragging a control on top of another control can leave the two controls shown overlapping on the design surface, even though a web page cannot actually contain overlapping controls. The overlap is only visual: the saved page, the running web app, and the reloaded project all show the controls correctly stacked. The designer corrects its display only after switching breakpoints, reopening the page, or making another edit. Resizing a control over another control shows the same problem.

Expected behaviour: when a drag or resize cannot be honoured because another control occupies the target cells, the designer snaps the control back to its real position instead of leaving it drawn on top of the other control.