As a quick follow-up, we use the HLS URL provided by Vimeo for all of our videos. For the videos that the HLS resulted in error, we swapped it for the MP4 URLs also available from Vimeo. (Make sure to adjust the videoType parameter from HLS to MP4, too.) This isn't ideal, as we now have a mixture of HLS and MP4 references, without any rhyme or reason, and we lose the benefits of the HLS streaming. However, all of our videos are back up and functioning. I wish that Roku had a fallback URL that could be added, so that if the HLS stops responding the direct MP4 stream could stop any errors.