Realtime Graphs Probblem

Hi Folks,
I have installed LuCI openwrt-18.06.1 on Tp-Link tl-wr840nv3 a while back ago.It has been working pretty well except for some Router inherited storage issues but recently I have to use "Realtime Graphs" all the graphs are working pretty well except "Realtime Wireless" not showing any data on both tabs.By the way I am using router as a wireless repeater.
I have included the console view of Chrome(I also used other browsers with same outcome).
One more thing how can I reduce time interval of all graphs to "1 minute window, 1 second interval" .
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Any help will be appreciated!!