When you try to run the rollup, you may see the warning about certificate revocation list,this is because Exchange tries to connect to the certificate revocation list (CRL) that has been issued by the publisher of the update rollup package or of the service pack. please adjust the IE settings to workaround the warning shown before you proceed with the roll up installation.
You should revert the IE changes once you have finished with the installation of the rollup.
Also ensure that you disable the Forefront Protection for Exchange before the starting the installation and enable it back after the successful installation to avoid any potential issues.
you will see a successful event after the clean upgrade of the product,
Windows Installer reconfigured the product. Product Name: Microsoft Exchange Server. Product Version: 18.104.22.168. Product Language: 1033. Manufacturer: Microsoft Corporation. Reconfiguration success or error status: 0.
I have tried this update on my LAB machines, and did not observe any issues. Also the installation went just fine, in less than 20 minutes.