Cannot watch a movie

We have a continuing problem when watching movies with Netflix, Prime, or on demand.The movie pauses or stop completely and then an error message, sorry we are having trouble connecting to the internet, please try again later. Sometimes even regular TV disconnects when this happens with a movie. We have called Comcast many, many, many, many times. They usually reset something, all is good for awhile and then it starts again. The line from the street has been checked by them and the technician said it's fine, so my assumption is it's in the house. I wish this could be resolved but we have been here nine years so far, not sure what to do but or who maybe able to determine what is wrong in the house.