When carrying out an in place upgrade to Skype for Business ensure that you do not start the services in a mixed mode fashion, upgrade all the Front End Servers in the pool and then execute the new “Start-CSPool” cmdlet, the cmdlet will start all the services on all the Front End Servers in the pool simultaneously, for all non user homed pools for example Edge and Mediation you can continue to use the “Start-CsWindowsService” cmdlet.
