At a customer I've updated the Primary Site Server to 1802, this went without problems. The customer has 7 sec.sites. From ConfigMgr Console I started the upgrade which failed. In ConfigMgrSetup.log it stated that the SQLSysClrTypes.msi failed to install (see attachment). This prerequisite was already installed on the server. Also the 'Microsoft SQL Server 2014 Management Object’ was already installed. Which eventually gave the same issue.
I've worked around the issue by removing the MSI Installer registrations of these 2 prereqs in the registry. The upgrade was now able to end successful.
Somehow the Upgrade sequence doesn't check if these 2 prereqs are allready installed, which IMO it should do.