Webpack bundle analyzer "+ n Modules"

In the webpack bundle analyzer UI, there is a checkbox where you can show the contents of concatenated modules. If you check that box, you will see the contents.

Here is what the UI looks like, where you can toggle the setting:

Here is what it looks like without the box checked:

Here is what it looks like WITH the box checked:

Sounds like you are using the ModuleConcatenationPlugin, try commenting it out. It's one of the plugins that can obscure this. Here are more details and the defect logged.