Strange behavior using view-based NSOutline (Sourcelist)

Question

I have a (new in Lion) view-based NSOutlineView as Sidebar SourceList in my app using CoreData + NSTreeController + Bindings + NSOutlineView and an Object as NSOutlineViewDelega

Answer 1

Setting setFloatsGroupRows:NO for the outline view must solve the issue with first group item moving up-down when being expanded/collapsed.