block twitch with FQDN not working with schedule rule

hi,
i setup a FQDN rule for twitch.tv
i've tested it with some computers in the company and it works.
i also set up a schedulde on this rule to allow access during the lunch.
but i found a bug.
indeed if you start a live on twitch during the granted time access, you can still use it until you refresh the page
so some of employees had noticed it and keep their page on the live stream to have it all the work hours....

any idea to fix it ?
i have Zywall 110 with 4.39