Need help with animation Matrix

For some reason, instead of using inherent blend animation, I need to invent my own.
For this, in the 'handleBlendSequence' function, I chose to input final matrix into
the smNodeLocalTransforms[nodeIndex] as follows.

void TSShapeInstance::handleBlendSequence(TSThread * thread, S32 a, S32 b)
{
.... // Get Key animation in thread
...
// apply blend transform 
      // previous smNodeLocalTransforms[nodeIndex].mul(mat); is multiple(blend) anim 
      smNodeLocalTransforms[nodeIndex] = mat;       
      smNodeLocalTransformDirty.set(nodeIndex); 
}

But as you can see in the following video, whenever I play the animation, the position
of the animation is not correct.



Do I need to do something before I input the final matrix into 'smNodeLocalTransforms'.
Or is there something that I'm missing?