I think the difference may be that you have the Group Headers styled vertically and I have them horizontally.
The original bug Ursula
posted also had the group headers vertically... so maybe that specific problem was fixed in July but a similar problem exists if the group headers are styled horizontally
(as in my 3 print screens) ?
In the video, the redraw problem goes away when I change the selected date. Other times it does not...
1 - Style the Month View group header orientation to horizontal
2 - Run the app and Open the calendar in Day mode
3 - Change to Month view
4 - See the draw problem on the 1st row
5 - Change to Day View
6 - Change to Week View
7 - Change to Month view
8 - See the draw problem on the 3rd row
9 - Change the selected date and the redraw problem goes away
Here is a link to the video
If this doesn't help then I'll try to put together a sample project