When using the Orthanc Explorer dialog to change the PatientID, I get an error when I only try to change the casing of some character of the Patient ID:
Error while modifying study tags: another patient with the same PatientID already exists. You should use the Change patient function instead.
More severe: If you follow this advice and use “Change patient” instead, it seems to allow this procedure, but the data seems to be deleted in the end. It allows this despite the fact that there is no other Patient with this ID (but this patient - if you ignore casing)
I have Orthanc version 1.12.6, Orthanc Explorer2 version 1.7.1
