OAuth 2.0 Flow: User Credentials cached

I am running into an issue when using different user credentials with the OAuth 2.0 flow.  

I have 4 users - whom use the same information to get a token (client id, client secret etc..) the only difference between these users is their username and passwords.  I have used the Authorization Code Grant before in the past and have tried the other OAuth 2 Flow Grants.

The problem persists after I have retrieved 1 token for a user.  After I have retreived 1 token for a user I then try and retreive a token for another user, and after I select the get token button the pop up does quickly closes and does not prompt me for my log in information and the token received is actually the first users credentials.  It appears that the user credentials are cached while the token is valid.  

I have looked online to find that other people have had this isse with earlier versions of soapui many years ago.  I am using ReadyAPI 2.1.0
https://community.smartbear.com/t5/SoapUI-Open-Source/While-testing-my-REST-APIs-the-previously-posted-request-details/m-p/105660/highlight/true#M18318

The documentation for this in Soapui does not give me enough information.

Can someone please help me with this issue?  The only other solution I can find is to use an automation script, that forces to the user to logout. 

Thank you,

Stewart Moon