I am NOT an expert at reading log files (usually I look to see if they have a supported GPU, and that's the end of my reading).
I did notice a lot of "Opacity" warnings like this:
[WARN] <MapExporter> The input map 'Opacity' needed by the map 'Mermaid_Dressed_Mat_BodyMain_BaseColor' of the texture set 'Mat_BodyMain' isn't available because: 'Opacity' channel is missing in your texture set.
[WARN] <MapExporter> The input map 'Emissive' needed by the map 'Mermaid_Dressed_Mat_BodyMain_Emissive' of the texture set 'Mat_BodyMain' isn't available because: 'Emissive' channel is missing in your texture set.
[WARN] <MapExporter> The map 'Mermaid_Dressed_Mat_BodyMain_Emissive' can't be generated for the texture set 'Mat_BodyMain'.
I don't pretend to have read to the bottom of the log file, but do you have an Opacity channel?

It seems unrelated to your real issue, but I thought I'd ask while we wait for inspiration (probably in the form of another person).
P.S.
Cool looking project. I hope it starts working for you.
P.P.S.
Have you tried the new version of Painter that came out today? 2018.1.1.