I'm not exactly sure what's going on here but I suspect it has something to do with the "peeled potatoes" being in your inventory. There are several tools in your inventory that peel potatoes so I think maybe one of them is wrong. Using the potatoes on the Y-Peeler (which Jobie claims to hate!) will work. Or that using the mandoline on the peeled potatoes removes the potatoes from your inventory which would also make this happen, I think. Luckily, you can actually skip the mandoline step completely! There are also still debug controls in the game so if that doesn't work "ctrl-s" will give you every inventory item which may also work. Plus, that would give you a look at some cut content and other weird and broken stuff!
EDIT: I think actually doing the thing you are instructed in-game to do is the problem. Don't shave the potatoes. (What a weird sentence)