The retargeted animations aren’t quite the same as the original. Hard to describe exactly what went wrong, but the retargeted animations look like someone not fully in control of their muscles. 
I’m curious which bones didn’t map correctly? That could explain the problem. The only bones I noticed not mapping was spine3, plus the custom and IK bones. There simply wasn’t enough bones in the rigify deform spin to have a hip, pelvis, three spines, and a neck.