I have a Firestick, but it is at our summer place. I may be heading out that way and if I do, I will pick up the Firestick and starting using it at home. If the Firestick does it, then the problem may be something Roku is not aware of. Could be to the point made previously, that a compatibility issue has been created on the sending end of streaming services.
What is a shame is that Roku has the currently popular business model of having nobody actually talking to a client with a problem over the phone. Being able to ask questions, have them try something, etc., while on the phone could get to the root of the problem.
Having been someone who spent a good chunk of his career troubleshooting power plant operational problems, I can speak with confidence when I say that intermittent problems are the hardest to diagnose. It is easy for us to sit here and whine about it and say things like "Why don't they just fix it?" It's another thing to be the guy that has to figure it out before he can fix it.