Symptoms
When a user is part of a role and that role is used as a destination, re-directing a work item to someone else, does not appear to work as expected.
Diagnoses
Redirecting a work item works when the destination is a user, so this seems to be role specific. I have spoken to the LABS support engineer and this appears to be a bug. (This happens in 4.6.11.)
Resolution
We sent the ticket to the LABS support team and K2 has logged an item for investigation in TFS. (This should be fixed in a future release.)