Configuration abc.config depends on abc extension that will not be installed after import

I have a problem trying to import a webform config.

• The form uses a custom handler that was written by my workmate in a custom module called xyz.

• In the module, it declares and use a config named abc.config for some reason, where abc is not the name of any module at all.

Unfortunately, years later, now I need to reimport some webform config into the same website. And everytime when I import the setting, the following error comes up:

Configuratin abc.config depends on abc extension that will not be installed after import

I've removed the webform's reliance on the custom handler. So the webform should not be depending on the module nor the config at all. But for some reason, the import still fails with the exact same message.

I start to feel there was a problem with the config existing under the incorrect name at all.

Does Drupal actually "thinks" that a module abc exists when a config abc.config exists in the system? Or is there other thing I should be looking for?