Make sure you don't have duplicated particle files ending in _0, _1, or _2 located in FeralHeart > media > particles. If you find these, delete them.
It could also be an issue with not having the temp map which looks like this:
Map maker might crash if it is not in the terrains folder. So if you do not have these, press the windows button, type Run, and then type in %temp%. This should recover your temp files with ease.