Map Markers blacked out

Markers placed in specific chunks of my world seem to be permanently blacked out. Making a new map, new banners, different colored banners or placing banners in different spots in the general location doesn't seem to fix the problem. On older maps generated in the snapshots all markers including map and player locations are blacked out, while newly created maps in pre-release 7 only have the banners blacked out in certain chunks. Banners placement range from buried underground to above ground with complete view of the sky. Hoping this isn't just a bug with my world.