Hello guys, I have the very same problem except in my file the arms become absolutely microscopic (very sweet like a baby squirrel but not what I need). If I scale the effect of motionclipblend down to zero the arms keep their reasonable size, but of course I need the effect. And if I swap the inputs the arms get monstrously big.
EDIT: Within the motionclipblend asset there's computetransform2 in the foreach-block. This is where the arms shrink that much. But I assume the reason is somewhere in one of the transform attributes that still exist before the motionclipblend.
So I found out I can not delete the joints I want to blend as Jeff does it in the tutorial, cause everything from the first missing joint in the hierarchy gets some messed up transformation data.
A way that worked in my scene instead is choosing the joints to blend in the motionclipblend Group parameter. That way no data needed is lost.
