Job failed with SORT020U: SORT(EXTSM) failed - sort engine status = 9/065

Dear All,

One of our job failed with the below error. 

SORT FIELDS=COPY
SORT013U: I/O error on dataset 'SORTOUT'
SORT014U: Status = 9/065
SORT020U: SORT(EXTSM) failed - sort engine status = 9/065

Please find the JCL below 

1 //NBAECOPY JOB (15541840NM),'PIN FILE COPY',
2 // CLASS=N,
3 // MSGCLASS=P
4 //*
5 //*****************************************************************
6 //PS0060 EXEC PGM=SORT
7 //*----------------------------------------------------------------
8 //SYSOUT DD SYSOUT=*
9 //SORTIN DD DISP=SHR,DSN=NMLP.P.N.TX.ALLEMP.PINS.LPX(0)
10 //SORTOUT DD DISP=OLD,DSN=NMLP.P.N.TX.ALLEMP.PINS.LPX.FTP
11 //SYSIN DD *

Verified that no locks. Unable to find the actual root cause of this issue. Please advice