rman active duplicate error out ORA-17628 and is successful when re-run

trying to rman active duplicate

datafiles are restored ok but fails while doing a archivelog restore..

the same script is successfull when re-run

log file below

RMAN>
Starting Duplicate Db at 09-JUN-12
allocated channel: ORA_AUX_DISK_1
channel ORA_AUX_DISK_1: SID=239 device type=DISK
allocated channel: ORA_AUX_DISK_2
channel ORA_AUX_DISK_2: SID=470 device type=DISK
allocated channel: ORA_AUX_DISK_3
channel ORA_AUX_DISK_3: SID=702 device type=DISK
allocated channel: ORA_AUX_DISK_4
channel ORA_AUX_DISK_4: SID=8 device type=DISK

contents of Memory Script:
{
   sql clone "alter system set  db_name =
 ''PYSYS'' comment=
 ''Modified by RMAN duplicate'' scope=spfile";