3362383 - SUM Error: 'RFC login to system failed with code 2 key RFC_LOGON_FAILURE' in MAIN_NEWBAS/PARRUN_SFW_UPG_LW_POSTPROC phase

Error occurred in phase MAIN_NEWBAS/PARRUN_SFW_UPG_LW_POSTPROC during upgrade using Software Update Manager (SUM):

Last error code set:
RFC login to system <SID> ashost <host> nr <number> gwhost <host> gwservice <service> failed with code 2 key RFC_LOGON_FAILURE:
Name or password is incorrect (repeat logon) 

Below error is found for client 'XXX' in 'PHASE_PARRUN.LOG':

Eg: RFC Login to: System="<SID>", AsHost="<host>" Nr="00", Client="120", User="DDIC", GwHost="<host>", GwService="<service>"
RFC Login failed
Exec with rc=-1

Also, the client 'XXX' found in above error exists in 'GETCLIENTSALL.LOG' as well:

Eg: START CLIENT:
SQL: SELECT MANDT FROM T000 WHERE MANDT <> '066'
"100"
"000"
"110"
"120"
Rows affected: 0
END CLIENT:

Note: In the above example, client 'XXX' refers to client '120'

• Software Update Manager (SUM) 1.X
• Software Update Manager (SUM) 2.0

Error, RFC login, failed, code 2, RFC_LOGON_FAILURE, Name or password, is incorrect, system, ashost, nr, gwhost, gwservice, MAIN_NEWBAS/PARRUN_SFW_UPG_LW_POSTPROC, phase, PARRUN, client, <sid>adm, Software Update Manager, SUM , KBA , BC-UPG-TLS-TLA , Upgrade tools for ABAP , Problem