Symptoms
Assume that you view a persistent chat room or a group chat (GC) room in Microsoft Skype for Business 2016, and then you click the link to show the participants. In this situation, the resultant pane starts getting too big, and you are unable to resize it.
Resolution
To fix this issue, install the January 3, 2017, update (KB3128049) for Skype for Business 2016.