Dragging between two (H5) grids sometimes does not remove underlying node #1612

Subject of the issue

Moving an item between two grids is not behaving as expected and leaving behind underlying nodes in the source grids engine. This is possibly related to / could be solved by containment being implemented in H5 dd.

Your environment

• 3.3.0 H5
• Chrome 86.0.4240.111

Steps to reproduce

Reproducable on https://gridstackjs.com/demo/two.html# by dragging an item from the left grid to the right grid, with the mouse somewhere on the right side of the item. This seems to occasionally trigger a race condition that causes and a placeholder for the item in both grids simultaneously.

Expected behavior

The underlying node should be correctly removed from the original grid.

Actual behavior

• gridstack.engine.nodes of the left grid does not remove the item.
• save() of the left grid contains the removed element.
• If the item is dropped back into the left grid, gridstack.engine.nodes will have duplicated the item. Causing strange resize/move and save()/load() behavior.