After you install the July 2018 cumulative update for Microsoft Skype for Business Server 2015, you may find that the following UCWA events are logged in the front-end servers:
UCWA encountered an unexpected exception during initialization.
An unexpected error has occurred during initialization.
Examine the exception details in the associated event log entry to determine the possible cause.
UCWA encountered an unhandled exception. An unhandled exception happened.
Restart the server. If the problem persists, contact product support.
UCWA encountered an unobserved task exception.
To fix this issue, install the July 2019 cumulative update 6.0.9319.559 for Skype for Business Server 2015, Core Components.