I would like to understand the issue better please. Creating relationships in Tracker should work the same way regardless of the DHIS2 deployment unless there’s an issue in the configuration or corruption in the DB.
Let’s focus on the error. Would you please share step by step how this issue appears?
I’m not able to reproduce this issue on Play. It says ‘constraint’ violation so there must be something in the details. One way to dig for more information about this error is to check the Catalina.out log. Please share the entire log (without the authentication / sensitive info).