dataRemovedBottom makes my grid load another page !

Hello, i'm using ui-grid and it's great, recently i found out a strange problem and i tried to solve it because i thought its my problem.

I have coded following this http://ui-grid.info/docs/#/tutorial/212_infinite_scroll and i have a strange jumping page issue. When i scroll down and load more data the grid works great but when i try to go up it seems to sets twice the scroll position and ask for another page.

You can see the issue here http://plnkr.co/edit/z7BRZD5akCpDzX11WNbF?p=preview , its the same plnkr as the original but i tried to increase the number 4 to number 10 in order to load more data.

when i comment out dataRemovedBottom line it works great but i cant decide if there are more pages up!

Thanks, i will come back with some feedback if i found something more.