I have been experiencing this same problem since the beginning of this month. The videos are hosted in a showcase on Vimeo. For the past several months I have had to add the direct video links from Vimeo to the json file I give Roku. The last attempt was to use a json file that was created by an online software my company uses to combine captions with the Vimeo videos. I have reached out to our IT person for help and to Roku, but just get advice to try the stream tester tool. If anyone else has experienced this error and knows of a remedy, I would be very grateful. Thanks.