Problem with net jitter

I have a very good computer and can play games on the highest settings 90% of the time. Also, I'm using wired ethernet internet via powerline adapters and have a ping of 20, download speed of 30 mbps and an upload speed of around 6 mbps. But whenever i play rotmg on flash i get a net jitter of around 200+ at times and rubberband around every 10-20 seconds. This game worked perfectly on my old computer but now on my upgraded computer it is unplayable. Please help

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Also, I tried clearing my cashe and reseting my router and switching to wireless connection, nothing works please help

Are you playing on flashplayer?