Skype for Business client becomes unresponsive when you join a meeting with many participants

Symptoms

Assume that you're running one or more Lync SDK–based applications on your computer, and you join a meeting that has many participants. In this situation, your Lync or Skype for Business client becomes unresponsive for a period.

Cause

Joining a meeting with many participants generates thousands of internal events, which are then queued and processed.

The presence of a Lync SDK–based application causes the Lync or Skype for Business client to send these internal events to additional queues. These queues use inter-apartment COM calls that take significantly longer to complete. While this queue is processing, the client UI becomes unresponsive until the queue is cleared.

Workaround

To work around this issue, exit all Lync SDK–based applications before you join a meeting.

Resolution

To resolve this issue, install the latest updates for Skype for Business 2016 and Skype for Business 2015. Then, create a GPO to add the following new DWORD registry key and set the value under the path:

HKEY_CURRENT_USER\Software\Microsoft\Office\xx.0\Lync

DWORD EnableLargeMeetingProcessing = 1
DWORD LargeMeetingMinimumRosterCount = 20 (default)
DWORD LargeMeetingRosterLoadingDelayInSec = 30 (default)

Alternatively, you can enable this fix by creating a custom policy entry and adding it to the client policy, as follows:

$x = New-CsClientPolicyEntry -Name "EnableLargeMeetingProcessing" -Value "true"

Set-CsClientPolicy -Identity "<ClientPolicyName>" -PolicyEntry @{Add=$x}