thanks for the pointers. Corporate ldap has two special characters in the password. And due to this, there were two extra "\"s in codebase\web-inf\map credential text file. Once we clean up the map credential file, the migrator is moving ahead.
In situations where you are using the same LDAP for both source and target, restarting the Upgrade Manager could remove LDAP entries.
See the below workaround developed by Datafrond Team, resolution logged within the Datafrond database. If you experience similar symptoms, try applying the below resolution.
Upgrade Manager Fails at Step: Execute Standalone Migrators
PTC Support Case 10540246 (Workaround)
Refer to an existing SPR 2095047, however differnet symptoms. Follow the below workaround for Customer until PTC provides a resolution.
Customer Symptom: Each time you exit upgrade manager, pending users node in LDAP gets deleted.
Workaround: As a pre-ugprade step, ensure that the pending users node exists in the Windchill DS. If doesn't load the pending users data has been modified to reflect the new domain - corp.cusotmername.com