If you can get into the CV to the point where you can issue online commands (the ENTER NEXT TASK CODE: prompt), try to see if there are any active user tasks (DCMT D AC TA) and if there are, cancel them (DCMT V AC TA TE TA taskid). If there are any batch jobs running batch-CV transactions against this CV, try to cancel them from the operating system. The IMMEDIATE option on the DCMT SHUTDOWN command will attempt to do the above before issuing the shutdown. If your shutdown procedure does not use IMMEDIATE, then try that. If none of this works, then cancel the CV with a dump and restart it - this should work fine. Presumably you will still want to have a clean shutdown, so then shut it down again straight away.
CV hanging at shutdown is something which should not happen, so open an issue with technical support and send in the dump for analysis.