Error while posting radiometricTarget

[Dryocopus]

I'm trying to load a radiometricTarget, but get an error:

Request:
[{"label": "TODO", "properties": [{"rdfType": "http://xmlns.com/foaf/0.1/Agent", "relation": "http://www.opensilex.org/vocabulary/oeso#hasContact", "value": "os-u:peter.roos"}]}]

Performing POST request...
URL used was: 'http://145.100.57.177:8666/rest/radiometricTargets'

Reponse:
Status code 500
{'status': 'INTERNAL_SERVER_ERROR', 'metadata': {'pagination': {'pageSize': 0, 'currentPage': 0, 'totalCount': 0, 'totalPages': 0}, 'status': [], 'datafiles': []}, 'result': {'title': 'Unexpected internal error - org.eclipse.rdf4j.repository.RepositoryException', 'message': '', 'stack': None, 'fullstack': None}}

When I set the rdfType to an empty string, the result is the same.

When I set the rdfType to null, it works, but the rdfType http://xmlns.com/foaf/0.1/Agent is suggested by the Swagger docs. It might be a documentation issue.