Javadoc Popup in Eclipse throwing error for methods/constructors for Windchill API

We are using Eclipse to develop Windchill customizations, but we're having some issues displaying the javadoc popup for Windchill's API.

For classes the popup gives me the javadoc information as expected, e.g. SearchCondition:

But when I try to get information about the constructor for SearchCondition the javadoc popup throws an error message: "Note: This element has no attached source and the Javadoc could not be found in the attached Javadoc."

Here you can see that the javadoc location is specified for the codebase:

As a workaround I can open the javadoc in the browser, but it would be great to access the javadoc directly in Eclipse. Is there a way to achieve this?