Round robin not working

Hi

I have load test with 2 client and 2 webserver with VS using source persist

when client1 access VS >> it's go to webserver1 (From this time client1 will access only ws1 due to source persist)

but when client2 access VS >> it's go to webserver1 too !! (and webserver2 have no connection cause all client access ws1 due to src persist)

Why client2 didn't go to webserver2 due to Round robin loadbalance method?

Thank you