Gunnar,
I tried your suggestion, created a repository with just the missing parent (jakartaxmlregistry-106) and attempting to deploy it. Unfortunately it fails with the error below. It would seem that we may be dead in the water unless Sonatype can provide some support. If you have any other suggestions I will gladly try them. Thanks
[INFO] RC-Releasing staging repository with IDs=[jakartaxmlregistry-1006]
Waiting for operation to complete...
..
[ERROR]
[ERROR] Nexus Staging Rules Failure Report
[ERROR] ==================================
[ERROR]
[ERROR] Repository "jakartaxmlregistry-1006" failures
[ERROR] Rule "RepositoryWritePolicy" failures
[ERROR] * Artifact updating: Repository ='releases:Releases' does not allow updating artifact='/jakarta/xml/registry/xml.registry-api-parent/1.0.10/xml.registry-api-parent-1.0.10.pom'
[ERROR]
[ERROR]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 53.982 s
[INFO] Finished at: 2019-09-09T15:14:00Z