Looks like I also ran into the same (or at least a very similar) problem with the Dokka plugin. The Dokka Gradle plugin depends on a shadow jar. When I publish the plugin normally, the POM file references the correct artifact ID for the fatjar. When I publish to the plugin portal, the generated POM references the name of the module from which the fatjar is built, and the plugin doesn’t work because no such artifact is published.
The worst part of this is that there doesn’t seem to be any way to test a plugin before I publish it, so I discovered the problem only after the plugin has been published. Now the plugin portal contains a completely broken plugin with no possibility for me to delete it until I find a proper fix for this issue.