OEM 12c Regular Daily TNS-12508 Alert for 10g Listener

Everyday at the same time, there is an OEM 12c alert for the 10g listener as below:

 Host=racnode1.raccluster
 Target type=Listener 
 Target name=LISTENER_racnode1.raccluster 
 Message=TNS-12508. Please check log for details. 
 Severity=Critical 
 Event reported time=Dec 1, 2016 5:41:19 PM EST

Information in LISTENER.log :

01-DEC-2016 17:34:21 * version * 0
01-DEC-2016 17:34:21 * version * 0
01-DEC-2016 17:34:22 * 12508
TNS-12508: TNS:listener could not resolve the COMMAND given
WARNING: Subscription for node down event still pending
01-DEC-2016 17:34:22 * (CONNECT_DATA=(CID=(PROGRAM=)(HOST=racnode1.raccluster)(USER=oracle))(COMMAND=status)(ARGUMENTS=64)(SERVICE=LISTENER)(VERSION=186647552)) * status * 0
01-DEC-2016 17:34:22 * log_directory * 0
01-DEC-2016 17:34:22 * trc_directory * 0

From LISTENER.log, most likely one command does not exist or failed while running against the 10g LISTENER.  Some doc said it is trying to run “show oracle_home” which is not available for 10g listener.  After this failing command, there are two successful commands against “log_directory” and “trc_directory”.

LSNRCTL> show oracle_home
NL-00853: Message 853 not found; No message file for product=network, facility=NL [ show] [oracle_home] [ show]

After manually running “show oracle_home” against 10g LISTENER,  I did NOT see “TNS-12508: TNS:listener could not resolve the COMMAND given” recorded in LISTENER.log as per Doc ID 1596633.1

WORKAROUND:

Suppress the alerts by changing the default threshold for “TNS Errors” metric from:

TNS-[ ]*0*(1169|1189|12508|1190)
to:
TNS-[ ]*0*(1169|1189|1190)

“Upgrading the Database Plug-in to version 12.1.0.6 or higher” as per (Doc ID 1596633.1) is NOT working,  since our  database plug-in is 12.1.0.8 already.