TabToNextAtEnd on TAdvColumnGrid

I have had issues with the TabToNextAtEnd on TAdvColumnGrid. I have, in one case, a panel containing three TAdvColumnGrids. All three are set for 
TabToNextAtEnd, and on the first two, that works fine. On the 3rd, however, tab simply moves between the two rows of that grid, and will not advance (or return) to the first grid.


If it makes a difference, the specifics of the third grid are that it has two rows, two columns, and only column 1 is editable. In both rows, a custom editor is used, which is a TColumnCombobox.