Scrolling down not working when dragging an element and simultaneously adding/removing components to the form

问题

When I am dragging an element down, the form doesn't scroll down when the dragging reaches the bottom.

The reason for this may be that I am manipulating the content of the form by adding an empty placeholder component under the dragged component, and then removing and adding the placeholder each time the dragged component moves over another component. I call revalidate each time the placeholder is removed/added.

Strange thing is that the scrolling works fine when dragging upwards.

Any suggestions for what could be the cause and how I may fix it?

Thanks

来源：https://stackoverflow.com/questions/51003540/scrolling-down-not-working-when-dragging-an-element-and-simultaneously-adding-re