In client operation mode, when i try to group on date it doesn't work properly the issue can be reproduced in demo also. I have attached the screenshot of demo page. In server mode i get the result as expected.
I have the exact same issue - I have a DateTime column and in the dataset of 200 rows there are only 3 unique dates. If the grid is in server mode then grouping works fine, if I put the grid into client mode then I get a group for every single row. Grouping by other columns seems to work okay. This is also still happening with the online demo - is this a known issue? are there any suggested work arounds?