Hi Celalettin,
If the users are supposed to be identified by cookies, it looks like a problem in the tested web application's authentication mechanism. However, there is also a small chance that the problem is caused by the fact that the problematic user's credentials are sent to the web server in some earlier requests (if some login operations which are not related to cookies have been performed earlier). To check whether this assumption is correct, please zip your entire project suite folder along with the log of the failed test execution and send us the archive via our
Contact Support form. Make sure that messages in your log correspond to the latest version of your tests.