sourcepath does not work with aggregate goal

In our project we use lombok.

For the JavaDocs we delombok the sources using the Lombok plugin and add the output directory (${project.build.directory}/generated-source/delombok) to the sourcepath option.

This works fine for the non-aggregated reports, but it does not work for the aggregated report, with the sourcepath configured the report simply never executes (no Generating "Javadoc" report — maven-javadoc-plugin:3.3.2:aggregate-no-fork).

Is this a know issue? Otherwise I can provide a project to reproduce this.