Two "sources" artefacts are produced during a release build.
A first one is created by the activation of the release-profile and a second by the maven-shade-plugin. Only the latter is created during a standard build.
Although the second overrides the first, both are attached to the build which causes a second attempt to upload/deploy the same artifact to the remote Maven repository. This is useless and may cause issues if the remote repository prevents release artifact from being overridden or if they were generated in the reverse order.
The build procedure should be reviewed to keep only the artifact produced by the shade plugin.
The same is true for the "javadoc" artifact.