ESSO -detects the page and sends login credentials, while the browser is still working to execute login to the application, SSO redetects the login page and executes it again.
To work around the problem, make SSO wait a few milliseconds, depending on the target application performance.
This can be done by the following custom script:
Send SSO Parameter (for Username)
Send SSO Parameter (for Password)
Click (on the related button object)
Sleep xxx ms (needs to be tested to find the best value)
Return (SSO done)