Hello,
You should select the study you want to add to a patient, select the destination patient and click the move button.
Or, in other words, merge the patients with the same patientid/issuer before changing the Patient Name, if you have several patient entries with the same Patient Id, due possibly by the use of a previous version where that situation was possible.
If this is not the problem/solution, maybe try to just change the config of dcm4chee.web service=WebConfig in the jmxconsole, enable trustPatientIdWithoutIssuer, it can solve problems with some fonctions when there is no issuer for the patient id.
Regards