'Could not lock request' during cancelling the concurrent request

Tried to cancel some long running requests in my environment and faced the issue 'Could not lock request'. Below are the steps I followed to fix this issue and to cancel those long running/hanging requests.

SELECT inst_id, DECODE(request,0,'Holder: ','Waiter: ')||sid sess, id1, id2, lmode, request, type FROM GV$LOCK  WHERE (id1, id2, type) IN (SELECT id1, id2, type FROM GV$LOCK WHERE request>0) ORDER BY id1, request;

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Column Manager   Format A12

Column Request   Format 999999999

Column Program   Format A30

Column User_Name Format A15

Column Started   Format A15

Column FNDLIBR  Format A9

prompt Managers that is running a request and FNDLIBR PROCESS;

select substr(Concurrent_Queue_Name, 1, 12) Manager,

       Request_Id Request,

       User_name,

       Fpro.OS_PROCESS_ID "FNDLIBR",

       substr(Concurrent_Program_Name, 1, 35) Program,

       Status_code,

       To_Char(Actual_Start_Date, 'DD-MON-YY HH24:MI') Started

  from apps.Fnd_Concurrent_Queues    Fcq,

       apps.Fnd_Concurrent_Requests  Fcr,

       apps.Fnd_Concurrent_Programs  Fcp,

       apps.Fnd_User                 Fu,

       apps.Fnd_Concurrent_Processes Fpro

 where Phase_Code = 'R' And Status_Code <> 'W' And

       Fcr.Controlling_Manager = Concurrent_Process_Id and

       (Fcq.Concurrent_Queue_Id = Fpro.Concurrent_Queue_Id and

       Fcq.Application_Id = Fpro.Queue_Application_Id) and

       (Fcr.Concurrent_Program_Id = Fcp.Concurrent_Program_Id and

       Fcr.Program_Application_Id = Fcp.Application_Id) and

       Fcr.Requested_By = User_Id and

       Fcr.request_id =&request_id;

select ses.sid,

              ses.serial# serial#,

              proc.spid,

              ses.sql_id,

              ses.process,

              ses.last_call_et,

              ses.event

         from gv$session ses, gv$process proc

        where ses.paddr = proc.addr and ses.process in ('&process_ID');

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