I was meant to update this. Its got me stumped. Currently running at 600m V5 for the past couple of days without issue. It could well be a problem with the Pi instead. But I don’t know. It works fine when it works. When the issue arose then it would take a couple of power cycles and then it would work fine on stock settings.
I would suggest removing all other sources of interference and working from the bare minimum to start. Replace the USB cable; they are notorius for failing and causing these types of issues. Try plugging into another processing unit or pc to see if the issue persists. Eliminate the Pi as an issue before moving on.
Yep tried three different cables all all experienced the same thing. Can’t try another pc as its windoze 10 and an arse.
Coincidentally this evening after knocking my desk, the cable moved and the problem started again. I’m going to take a look at the micro usb socket on the board and see if I can replace it.