With that out of the way, I wanted to point you over to the TV Answer Man by Phillip Swann. He covers a question about Netflix buffering pretty well.
A reader of his Website asks about why there is so much trouble with the picture on Netflix so often. And Mr. Swann's answer is a good one.
There’s an obvious reason for this problem. Your Internet service’s speed varies and sometimes it will dip below the minimum requirement for a high-def or 4K picture.
(Netflix says you need a minimum speed of 5 Megabits (Mbps) to watch high-def and 15 Megabits to watch 4K programming.)
When this occurs, Netflix may post an on-screen message asking if you want to change the HD setting to SD, or the 4K setting to HD. I would not advise doing this very often. You are paying for HD and/or 4K and you want to watch your show or movie with the best picture quality possible.
He also points to another article he wrote about improving the situation regarding buffering.
I'll jump in and tell you how I solved the problem. I got a good network setup. You see, many times the equipment that ISPs provide is not good quality, and can impact the wireless signal. I got a good mesh network setup and solved all my problems. Good coverage means good coverage. No, it's not cheap. But it works, and my Streaming Life is the better for it.