Not a problem, that is how it’s supposed to be!
I really don’t think this is a rigging toolkit bug at all. I will take a look at files, but an FBX crash on engine side is likely not an issue with maya tools.
still looking into it, but my first guess is that this only opens in maya 2016, so I think it’s fact that fbxs are 2016 version. I need to test this theory, but I need to go eat lunch 
Ok, I’ve finished digging into this, and issue is definitely not with Animation and Rigging Toolkit, but rather with FBX version. When I tried to open provided FBX files, they would only open in 2016 for me, which was a red flag, as I don’t think UE4 has 2016 FBX fully supported yet. I simply re-exported FBX using FBX 2014/2015 file format, and presto!
I recorded process here: