The bug

When taking an expanded map out of the crafting result slot, any remaining papers in the crafting grid get updated with the incorrect stack counts

To reproduce

This can be reproduced in Creative mode.

1. Get a map
2. Get a stack of papers
3. Open the GUI of a crafting table
4. Put the map in the centre slot of the crafting grid
5. Drag across the remaining eight slots using the scroll wheel to them with paper
6. Take the resulting map, and put it back into the centre of the crafting grid
7. Repeat that as long as it is possible
   → At some point, the paper stacks will display incorrect stack sizes.

Original description

This isn't anything major as it is just a visual bug, but when you go from a base map and expand to the largest map right away, as you craft the new maps eventually the paper in the crafting slots will begin to duplicate, but if you remove the map once you're done the paper returns to what it should be.