I also have the same issue. I think the problem occurs because of the way Skybox VR handles the files. My assumption is that Skybox VR tries to crawl all the videos inside the current folder, which causes issues if we have, for example ten 8K videos with high bitrates.
When I tried using 4XVR, it only crawled the currently playing video, not all the videos. I know this because the files didn't show any thumbnails, only the file format icons.
To optimize it, I think it would be a good idea if Skybox VR gave an option to only crawl or read the files after the user opens the video.
Also, additional information: sometimes Skybox says the video can’t be played, but when I tried remounting my SSD, it played completely fine
