Inconsistent behaviour of dataRemovedBottom

Hi, team. I've found out a strange behaviour of infinite scroll with data removing. I've got the infinite scroll application example from the tutorial and modified it:

http://plnkr.co/edit/fX2sUVuv6zMhazIlM8lH?p=preview

The grid should contain only 400 rows at once. I'm performing the following steps:

1. scroll down until 699th row is uploaded;
2. move a scroll to the top, 200-299 rows are uploaded and then there are several scenarios:

• the scroll stays at the top;
• immediately 100-199 rows are uploaded, the scroll stays at the top;
• sometimes the scroll jumps down to the row which was the higher before new rows are uploaded.

Then it is possible to repeat the 1st and 2nd steps and it behaves in any different way.