I was having this same issue for well over a month, but it seems to have been fixed by doing a 'System Refresh' from my Xfinity set-top box. I've yet to find anyone else online who's done this, so hopefully this helps others. Not sure if this feature is new or has been there for a while, but I hadn't seen it or used it before. The option is explained here: https://www.xfinity.com/support/cable-tv/x1-system-refresh/
Basically, go to Settings > Help > System Refresh. Your box(es) will be unreachable for about ten minutes.
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