If the path of a specific module file is not set in the sitecore.

 The sitecore.json file is the project configuration file that contains several properties, including a modules property that references the relevant Sitecore Content Serialization modules. If the path of a specific module file is not set in the modules property, the SCS system will not be able to locate and access the module file, which contains the items to be serialized. Therefore, the paths and related items included in the module will not be serialized when you run a push or pull command. This can lead to missing or inconsistent data between the Sitecore instance and the file system. References:

Sitecore Content Serialization structural overview

Create a Sitecore Content Serialization module