LDEV-1817: Define later branching was breaking Preview. Now the preview hack allows it to be used with Random Grouping and this required regetting the grouping at one point to avoid a CGLIB class cast exception (hack on hack). Bleah.
The chosen grouping now works as I clear the number of groups before creating a group (and then allocating to a branch), otherwise I could run into the max number of branches test. Another hack.