We have DSL.
We were having constant problems with it last year. Then we had an internet problem, and a tech came to our home and switched out the modems and from then on it worked like a charm.
Then, a few weeks ago we had an issue with the server on the internet and my husband called the phone company and the tech had him changing all the settings and so forth. My husband got a supervisor on the phone who was able to fix everything.
But since then, we have had this issue. Yet, we watch other things on ROKU, like the Blaze network talk shows, and also some old TV show and it works fine.
It is not pleasant to watch a movie when it is buffering every few minutes.