Assume that you join a meeting without audio in Microsoft Skype for Business 2016 or Skype for Business 2015 (Lync 2013). When you call in to the meeting after the join, you may find that a second call to yourself is initiated. In some cases, a call may be initiated to yourself instead of joining the conference audio as intended.
Note This issue occurs only when the Skype for Business client is configured to join meetings without audio. Clients that are configured to join meetings with audio do not experience this issue.
To fix this issue, install one of the following updates:
For Skype for Business 2016, install the April 3, 2018, update (KB4018323).
For Skype for Business 2015 (Lync 2013), install the April 3, 2018, update (KB4018334).
Note Lync 2013 was upgraded to Skype for Business in April 2015.