Hello Sigrid.
Yes, we have a wedispatcher. But we don´t have Webdispatcher Admin, however the URLs are maintained in SICF.
We have checked the information of KBA 1866327 but was not possible identified the sessions´s origin.
We have tested it in a single application server, logging on as an agent and the sessions don´t close in either situation, logging off or closing the browser.
When we tested it, 40 sessions were created.
If you want please check the customer message number 1163373/2013.
Thanks. Kind Regards 
Kattya Mejia