Yes bud same here, defo ISP related, these 4G pro routers look great but extra say £15 is cheapest i could see for unlimited data, i would isolate the firestick then hardware to the router for 4G
But extra costs not really cost-effective i suppose at present
I've set every device to auto connect to the vpn now but think it might have been too late as Sky had already identified me as an illegal streamer. I'm due a change of isp later this year so I'll probably change and keep every streaming device connecting to vpn on startup and hope that keeps me under the radar.
Trialled various networks for 4g in my house and none give consistent speeds, especially in an evening, so will just connect to the Mrs phone (ee) when needed for now.