The option dependency-track.updateParent fails if you (like us) have set the name parameter on all Maven projects to something human-readable.
The problem is that the project in Dependency-Track is created with artifactId as name, so it fails to find all our projects.
However, by changing the line
@Parameter(defaultValue = "${project.parent.artifactId}", property = "dependency-track.parentName")
private String parentName;
in UploadBomMojo it works with our projects as well.
Thing is, Maven inserts artifactId into name if it's not set, which explains why it works in all other cases.