Odd distortion in Blender FBX exported animation

So, I was busy developing a passion game, and BAM.

FBX exported animation seems to be causing a distortion at the legs of my mesh @

The animation is perfectly normal in blender and in the default t-pose that he was imported in.
See video for more information:

Am I exporting something wrong, or am I importing something wrong?
Not sure if it makes any difference, but I have Force Root Lock on my animation.