Doesnt consistently playback

I get a ton of lag while trying to stream my downloaded shows. I have to download them to my device to watch them seamlessly. If they could get playback to work well, would be 5 stars. Very frustrated with difficulties streaming. Problem isnt my internet or 4g because Netflix and amazon playback is solid.

Smmmmmmmmmmmmmm about Xfinity Stream, v4.4.0