A:Answer Try another router, say at a public place, friend, public library. Just be careful of someone sniffing the line, aka try enough to test, change passwords of any online service you used on a public line, with no encryption.
We use a VPN in public places.
Settings like Airtime Fairness, beaming, QOS, 20/40/80 wide channels, can cause all kinds of problems.
You need to rule out the router. I have one that has a ton of settings, some defaulting to not the best. It’s very fast, but a pain to sort out. The problems of giving you the kitchen sink, all the plumbing.