Twice I tried the latest release or beta builds and went back to v1.1.2 for various reasons. Both times after downgrading many of the thumbnails were corrupted. Refreshing or clearing the cache or uninstalling did not help. The first time I did a factory reset in Skybox - worked. The second time I deleted the videos off the headset and reload the files from my desktop via USB - worked.
Is there an easier way say deleting the thumbnail cache only from the headset? I tried snooping around with Sidequest and Windows file explorer but couldn't uncover anything.