Anet done helping? anyone seen this problem
What you describe sounds very much like delays or packet loss on the network between you and ANet. (Which is not necessarily the component owned by your ISP, btw, so even if that is perfect, it could still be an issue.)
https://www.pingplotter.com/fix-your-network is a guide to finding out where the problem is, so I’d suggest you look into that now — especially if, as you say, ANet support have exhausted their ability to assist you.
Thank you for the suggestion