Hello there,
Today I discovered something that seems to be a bug : In Cards view, we cannot move a card to an empty column (anymore ?). Only already populated columns seem to accept cards.
Note : It is not possible even when trying “above” or “under” the “New card” zone.
Is that a regression ? I think I was able to do that in the past 
Actually, I see another regression that looks similar :
Drag and dropping a table in the “New page” button (in the doc pages menu) also fails to create a new page with the table inside.
HTH
I experience the same behavior. Also tried clearing cache, cookies and restart Chrome browser. Drag and drop into empty columns is not possible anymore.
It seems those issues are solved now. Thank you !
(Note : If Coda team use those topics to solve bugs, it would nice to notify us of the results 
)