LN down when ST voip call is closed by other party

I use SameTime VOIP. With LN 8.5 I have a problem when the person that I called ends the call. I can then not switch to the sametime call screen to end it. In the task manager the voip goes to not responding. When closing it in the taskmanager, LN goes down completely. I have not had this problem in LN 8.0.