Default mutators in the official maps are different from the default mutators when creating a map.
Windows 10 64 bit, 8 Gm RAM, Intel(R) Core(TM) I7-4500 CPU1.80 GHz 2.40GHz GPU: AMD Radeon R7 M265, Intel(R) HD Graphics Family. Version game 1.5.1f5
1. Default mutators in the official maps and when you reset the mutators:
2.5. Base mana modifier: 0
Why create a new map, it is already mutators that differ from the standard? Fix it!
War for the Overworld Launcher Log.txt
We will look at fixing this in a future update, for now you should be able to load the defaults preset before you export the map.