Hub 5 high latency and jitter

This issue only started last week. I noticed I couldn't stream BBC radio stations at 320kbps without constant stops and starts. My Hub 5 is in modem mode connected to a TP Link router and I also noticed the router ethernet LED frequently changing from green to orange. I contacted Virginmedia who said they couldn't find any faults using their speed test because the Hub was in modem mode. I ran the Cisco Real Speed test myself and found very high latency and jitter. after unplugging the Hub for a minute or so (a very quick on/off didn't fix the issue) my latency levels were back down to around 20-25ms and I was happy. Until today when the same symptoms appeared. This time I checked the speed directly at the Hub 5 ethernet output so Virginmedia couldn't blame my router and here are a few measurements

I then switched off the Hub for a minute and after restart I measured this

So what is going on. I do not want to have to unplug the Hub every few days and the first warning I get of the issue is my morning alarm streaming Radio 2 fails to go off.