I started testing parts of the snapshot. When I was looking at one of the Explorer maps after trading one from a spawned in villager, I thought of testing changing the scale of the map. When I did this, the land outlines were removed.

To reproduce:

1. Open Minecraft in version 16w39a.
2. Trade with a villager that is a cartographer by occupation for an explorer map.
*If viewed now, the map shows shadowy lines for landmasses.
3. Change the scaling of the map by surrounding it with paper in a crafting table.
*If viewed now, the extra landmass lines are missing.