Caer Blaidd, Wolfpack's Den - Dropped only 2 maps (should be 4)

The map says "Unique Boss drops 4 additional Maps", and only 2 dropped. I have no clue why, and I doubled checked over my filter.

On a side note, map drops from map chests are quite weird since 3.9. I dont know what is going on. Sometimes nothing drop at all. I don't know if the issue is related tho.