There is a problem with grouping of columns. I have put a small sample project. On 1.10.1007 all works normally. This problem has started to arise on service release 10.1.2027.
I have put screenshots.
I have got the same problem...
the Bug disappear's after the DataSource gets applied a second time when the Grid is already shown.
That's a CRITICAL BUG for us because lot's of Customer's are using this Function!