When you shift a map in the chest gui(redstonchest,enderchest and normal chest) there are two maps in the inventory. But when you move other items the maps are not longer there.
EDIT: You also can duplicate the maps when you close the chest gui
MC-129237
map guest item
Resolved
Cannot Reproduce
1
Cannot reproduce in 1.13-pre2. If this is still an issue for you, please provide a small video with the debug screen enabled (hit the
F3key) demonstrating the issue.