I am getting a script core error at this function Screenshot - bc13e443db32a60b03d68549990a624d - Gyazo when I open the BigUpdateFeatures map (happens at this time Screenshot - 03b686b15ab2fbdb15b47cab7db33e51 - Gyazo).
I am using 4.12 preview, and I know it isn’t supported yet, I just wanted to let you know. 
I haven’t tried any of the other maps yet, I’ll edit this post by then.
EDIT: Every map except ForestDemo fails to load with the ScriptCore.cpp error.
EDIT 2: It happens in ForestDemo when I play it, so I’m guessing it’s something like the tree/plant blueprint that’s causing it.