Just a guess, I think your quaternion interpolation is broken. Maybe try disabling it and see if everything else works correctly?
Yeah, it has to do with the interpolation of the joint orientations. One thing i tried is glm::mix( joint0.m_Orient, joint0.m_Orient, fInterpolate ); That stopped the glitching but causes twitching as it isn't really being interpolated anymore. It appears that there is something wrong with the way glm::mix is handling things. I even checked the value of fInterpolate and that seems to be working correctly. Here's the current code.
finalJoint.m_Orient = glm::mix( joint0.m_Orient, joint1.m_Orient, fInterpolate );