Directories and/or folders can contain single parts which are part of an assembly. In this case the assembly must also "receive" a new directory name. Otherwise the assembly can no longer "find" the single part and therefore the assembly can no longer be assembled.

Therefore, at assemblies, activate the option field Adapt links in assemblies and enter the Assemblies path (Browse ...) in which the assembly can be found. Please keep in mind, however, that this procedure may take a lot of time!

I case you have not yet saved changes made within a directory tree, first the Save All window shows up. Save the desired changes before you rename the directory.