On these tumblers the "full" background option is not working so you can't add a seamless pattern. Here is what I mean in this picture below. Just wanted to let the Zazzle team know.
@wheresthekarma Have you filled the front layer with white? Check the background of the front layer
I've just transferred a design and it auto fills the background of the front layer.
Once I cleared it, the Full background layer tiled as expected
