Steps to reproduce:

• In creative mode, get a map from the creative inventory and open the map.
• Get a crafting table and paper.
• Middle click and drag around the map on the crafting table to get a stack of 64 around it.
• Take out the new expanded map and put it back in and repeat until the map has been used in the crafting table three times.
• The paper in the crafting table should appear to have stacked to 120 - 122