Hello,
I'm checking with an environment engineer to see if this would pertain to CU3 and 2018.
I found the following for bug 35988, its not fixed, so it wouldn't be in the install guide (it's not)
To allow the update to be installed correctly:
On the client machine, prior to the installation of the update, open the Command Window as Run as Administrator.
Map the drive to the parent directory using the same drive letter as the original install - e.g.
net use X: \\servername\installdir
(Note the space between the drive letter and the path.)
The drive letter must match the entry in the registry key for the INSTALLDIR and ParentDirectory entries.
Run the CU install.
These steps address the issue if the registry keys were not written correctly (e.g. the steps above were not performed):
To work around this issue, edit the appropriate registry entries to add the mapped drive path to the Dynamics SL program files location.
Warning Serious problems might occur if you change the registry incorrectly by using Registry Editor or by using another method. These problems might require you to reinstall the operating system. Microsoft cannot guarantee these problems can be solved. Change the registry at your own risk.
Use a registry editor to modify the following registry keys:
HKEY_LOCAL_MACHINE\Software\WOW6432Node\Microsoft\DynamicsSL. Edit the INSTALLDIR and ParentDirectory subkeys to the mapped drive path location to the Dynamics SL program files.
HKEY_LOCAL_MACHINE\Software\WOW6432Node\Solomon\SolomonIV Tools for Visual Basic. Edit the ParentDirectory subkey to the mapped drive path to the Dynamics SL program files.
For example when Dynamics SL is installed in the default program files location on the server, the SL folder is shared and the Dynamics SL client is installed on a computer that has the S: mapped drive set. Edit the appropriate subkeys to: S:\Applications
Best Regards,
Jana MacDonald
Microsoft Dynamics SL support