When input DICOM file is: [...] (0008,1030) UN (no value available) # 0, 1 StudyDescription [...] (0008,103e) UN (no value available) # 0, 1 SeriesDescription [...] The WADO-RS generates: "00081030" : { "BulkDataURI" : "http://acme.corp:8042/dicom-web/studies/1.2.3/series/4.5.6/instances/7.8.9/bulk/00081030", "vr" : "UN" }, [...] "0008103E" : { "BulkDataURI" : "http://acme.corp:8042/dicom-web/studies/1.2.3/series/4.5.6/instances/7.8.9/bulk/0008103e", "vr" : "UN" }, I believe the empty DataElement should be handled differently (even in the case of UN).
Thanks for the report! This is now fixed by the following changeset in the core of Orthanc, that will be part of forthcoming release 1.9.3 of Orthanc: https://hg.orthanc-server.com/orthanc/rev/9f7eef20bc7d