as is heard this is due to limited height of applications and when widgets are placed outside of that boundaries.
it seems to be not the case on your side, but it has exactly the same behavior as I experienced and reported to the support.
This is the answer from support:
I’d like to provide you with an update on this issue you have been seeing. It looks like this problem is only occurring when the height of your page is exceeded by the content. To clarify, adding to the list on the right increases the content of the page past the height set for your page (480px). When the list exceeds this height, the page begins to scroll. When this happens, the “Move” action shown in this screenshot below is not firing correctly.
This problem does seem to be a bug, and our team will file a bug report for this and work towards correcting the problem. To work around this problem, however, you can remove the height and only have a page width set up. Making this change should prevent the bug from happening. Please see the attached copy of your file with this change, and please let me know if this has helped!