Looks like we can't reproduce the issue or there's a problem in the test case provided.
Grid title using headergroup moves from center to top while sorting
In a grid using a header that spans two rows the title moves to the top when you click the header to sort the column. (Chrome 19, Fx 13, IE8)
Dunno, if it is this, what u mean:
Move mouse over header of Date column -> the text "Date" jumps to the top of the header and stays there no matter what.
Win7 64bit; FireFox 17.0.9 ESR
If that is the bug you are referring to, this has been fixed and is working correctly at least in 3.0.6: http://qa.sencha.com:8080/examples-3...ggregationgrid