ORA-17628 ORA-19505 during RMAN duplicate from active (non-OMF to OMF)

I'm trying to RMAN duplicate a database with non-OMF files to one with OMF (ie. with a db_create_file_dest parameter, so I don't have to think about filenames anymore).

However, my rman command below, results in a ORA-17628: Oracle error 19505 returned by remote Oracle server. MOS note 1331986.1 indicates I should add a translation parameter, but my command still fails. Is there a 'debug' log where we can drill down to find exactly which datafile was the offending one?

My RMAN duplicate command:

=======

run {
allocate channel c1 type disk;
allocate channel c2 type disk;
allocate channel c3 type disk;
allocate channel c4 type disk;
allocate auxiliary channel a1 type disk;


duplicate target database for standby from active database
spfile
  parameter_value_convert 'PRIM','STBY','PRIM','STBY'
  set db_unique_name='STBY'
  set db_create_file_dest='/stby_data/oradata'
  set db_create_online_log_dest_1='/stby_recon/oradata'
  set db_create_online_log_dest_2='/stby_recovery/oradata'
  set db_file_name_convert='/prim_data','/stby_data'
  set log_file_name_convert='/prim_recovery','/stby_recovery','/prim_recon','/stby_recon'
  set cluster_database='false'
  set control_files='/stby_recon/oradata/control01.ctl,/stby_data/oradata/control02.ctl,/stby_recovery/oradata/control03.ctl'
  set log_archive_max_processes='5'
  set fal_client='STBY'
  set fal_server='PRIM'
  set standby_file_management='MANUAL'
  set log_archive_config='dg_config=(PRIM,STBY)'
  set log_archive_dest_2='service=PRIM ASYNC valid_for=(ONLINE_LOGFILE,PRIMARY_ROLE) db_unique_name=PRIM'
;
}