I got a stacksize for example on the Garage door of 15 but as you can see they stack to 5 then the next craft they don't stack at all or they stack on 2 or 3 trying to move those items on top of eachother doesn't work they won't stack but If I drop them they will stack to their max stacksizes.
 

EDIT: I checked if it was because of the skins but even with the default skin it doesn't stack correct