What format was the video you were trying to upload? The video upload initially goes to a DTube server for re-processing (they generate a few different resolutions of video, and upload them to IPFS), and if the video is a non-standard format, or not in a format that's stream-friendly, that may be part of the problem. If it's not already an MP4 format, maybe try converting the video to MP4 and then try uploading that video and see if that works better?