Hi GGV,
I'm not sure, but here is my quick idea.
You can see timeout value in <RA root>/webapps/datamanagement/WEB-INF/web.xml on NAC like following.
In this example, timeout is 30 minutes.
<session-config>
<session-timeout>30</session-timeout>
</session-config>
You need to restart RA server service after update the file.
I hope it works fine.
Thanks
Yas