Xfinity stream app periodically not responding to Roku remote

I've been using the Xfinity Stream App with my Roku for a long time with no issues with the remote. Recently (last few weeks maybe?) I've been having an issue where, sometimes, after I've been watching a show for a little while, the app stops responding to my Roku remote....I can't pause, rewind, back out of the show, or anything! The only thing I can do is to hit the Home button to exit the app and go back to the Roku home screen. I can then go back into the app and it works again, at least for a while. Sometimes it resumes my show right where I left off, but sometimes it resumes from a MUCH earlier point, or even the beginning, so I don't dare do that if I'm far into the show. If the show has no commercials, I feel trapped -- can't go to the bathroom or anything -- it feels like I'm back in the old days before DVRs and watching a show on PBS or something, with no way to take a break or play a bit again that I missed because something distracted me!

I've tried rebooting my Roku, but it makes no lasting difference.

Please fix your app soon!

(P.S. Why do I have to choose "Xfinity Stream Website" under "Topic" -- why is there no option for the app??