I put my map onto the token layer by accident, then moved it to the background layer using copy&paste+delete. Now it has a turn, but I cannot edit it to disable the turn checkbox.
BTW: The layer selection UI is not very intuitive. Maybe the 3 layers should have selection tabs besides the "pages" pull-tab? That way you won't need to interact to check which layer is active, and it also saves one click and one mouse positioning when changing the layer. Same goes for zoom; make it a slider and put it in a drop-tab at center-top.