Getting unusual workflow mailer errors WFE_DISPATCH_RULE_ERR related

Getting unusual workflow mailer errors WFE_DISPATCH_RULE_ERR

ORA-01403: no data found' encountered during execution of Rule function 'ap_payment_event_wf_pkg.rule_function' for event 'oracle.apps.ap.payment' with key '59144'.

Event Error Stack:

Wf_Event.dispatch_internal()

Checked version of appewfpb.pls as advised in link below...seems current.  

http://oracler12applicationfunctional.blogspot.com/2015/06/workflow-error-in-ap-payments.html

[oracle@oraclep ~]$ cd $AP_TOP/patch/115/sql

[oracle@oraclep sql]$ strings -a appewfpb.pls | grep '$Header'

/* $Header: appewfpb.pls 120.4.12010000.5 2015/05/21 09:50:04 npendeka ship $ */

Any ideas?  We upgraded from EBS 12.0.3 to 12.1.3 on 12/11/15, rdbms upgraded from 11.2.0.3 and 11.2.0.4.  Discovered yesterday that a process that converts expense reports that have been audited by Finance into invoices was paused during upgrade and hadn't been set up again until yesterday...then these workflow mailer errors started.