The thumbnails of previously created designs do not update when you overwrite/update the design online.

Let’s say you had created a design before using the Voxel Editor and had saved it online. If you load it, make changes to it and overwrite/save the design file, the thumbnail of it won’t change and will be stuck on the thumbnail of the designs’ first version.

The item – it has the a thumbnail resembling the first version of the design even though, its’ changed since then:

Final version of the item, or what the thumbnail is supposed to be showing/rendering instead: