I had that same problem. I'm trying to see if CBS can resolve it, but I had to quit my subscription so as not to pay money for something I can't use.
I'd started a thread here, too, if you want to keep an eye on that one. Maybe if we keep making noise, someone who works for the company will see. I think it's an issue that CBS and Xfinity need to get together to resolve.
Temp fix....I found tht if i exit the App and go to settings in the fire "cube" .Apps>Installed apps and clear the cashe for some of my other apps and delete some apps we never use ...when i go back to the cbs all acces it works....for a while.
There is clealy a buffering problem . if you just turn it off and o it does not clear up the problem. but if you make a change to your "cashe" or your system memory it temporaily clears it up.
I have not tried resetting the cashe just for cbs all access..
the buffering issue comes up again halfway through the next show i watch...
I was able to get though Picard this way but once my free trial is done, so am i .