Filmstruck streaming interruptions

A couple weeks ago I tried signing up for Filmstruck (movie streaming service) and found it completely unwatchable.  Constant buffer interruptions every minute or two. Has anyone else tried it and had a different experience?

Its troubleshooting guide states that you just need 3 mb/sec download speed for HD streaming.  I have "essential internet service", no splitter, no router, no wi-fi, and I've tried disconnecting all other devices, and still constant interruptions.  In fact I've noticed that over the past year, even just youtube videos suffer constant interruptions.  I don't recall having any of these problems when I first signed up with Cox years ago, and I'm paying a lot more a month now than I was then. 

I don't see any purpose to upgrading to a faster service since there's no actual guaranteed minimum speed.  Any suggestions before I give up and switch to DSL or something else?