I found the above picture's behavior when resizing the window on both the 8.40.14 release. This is on the auto width. When you make the frame width smaller, the row header column starts peeling away from the table and leaves this gap. This is especially predominate with the auto sizing width and very long row header names.
Here is the same table with a larger width:
And here it is beginning to "peel" away from the table: