Symptoms
Assume that you open a group chat window in Microsoft Skype for Business 2016. When you click the Search button in the lower-left corner of the window to open the Search Chat Room History dialog box, you find that the dialog box has too many controls, and it pushes the OK and the Cancel buttons off the visible bottom.
Resolution
To fix this issue, install the May 9, 2017, security update (KB3191858) for Skype for Business 2016.