Hi Mohammad,
Thank you for sharing the result of the queries - they clearly show TSD_maint has the required alias.
If the same error is occurring "... User 'TSD_maint' is not aliased to dbo for database 'TSD'..." then I can only think of a couple other possibilities.
1) It's a bug in the DR Agent
2) The DR_admin user does not get the same result as you for command "sp_helpuser 'dbo'"
3) The DR Agent is connecting to a different server.
If you have capacity to share a copy if the DR Agent log file that contains the error, I can take a look and see if I find anything else useful.
Regards,
Stephen