We use v15sp4 actually and found serious bugs in call routings. External incoming calls are routed to a call group. Once a user answers and invokes a blind transfer to another user and the ringing times out (eg. after 1 minute), the call is routed back to the whole ring group instead the person which performed the blind transfer. In addition, not even the display of the caller is right when performing a blind transfer. There should be shown the number of the external caller in this case once blind transfer was invoked. Actually it shows the internal caller which berformed the blind transfer, quite useless.