Thanks for your report. To provide some details on what happened here, we recently released an update to use the MeshPart version of accessories in thumbnails instead of the SpecialMesh version. This lead to some of the thumbnails of some old accessories which had MeshPart versions with the ThumbnailCamera setup incorrectly to break. We have reverted this change and invalidated all thumbnails that were affected by it. Any thumbnails that still appear incorrect (like the ones still listed) were likely always bad and will need to be addressed manually.