I was hit with an issue when trying to update to Visual Studio 15.7.2.  The installer reported that it could not update itself:

Unable to install the files to target location. Error: The folder 'C:\Program Files (x86)\Microsoft Visual Studio\Installer' or a file within it is locked by another program. Close any applications that might be using it and try again.

The solution was to rename the installer folder (C:\Program Files (x86)\Microsoft Visual Studio\Installer) and to run the installer from the renamed folder.