I have a situation with using the animateMotion element.
Somehow the path to follow seems  off.

For example.


<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!-- Created with Inkscape (http://www.inkscape.org/) -->

<svg
   xmlns:dc="http://purl.org/dc/elements/1.1/"
   xmlns:cc="http://creativecommons.org/ns#"
   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
   xmlns:svg="http://www.w3.org/2000/svg"
   xmlns="http://www.w3.org/2000/svg"
   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
   xmlns:xlink="http://www.w3.org/1999/xlink" >
   width="744.09448819"
   height="1052.3622047"
   id="svg2"
   version="1.1"
   inkscape:version="0.48.3.1 r9886"
   sodipodi:docname="New document 1">
  <defs
     id="defs4" />
  <sodipodi:namedview
     id="base"
     pagecolor="#ffffff"
     bordercolor="#666666"
     borderopacity="1.0"
     inkscape:pageopacity="0.0"
     inkscape:pageshadow="2"
     inkscape:zoom="0.35"
     inkscape:cx="-262.14286"
     inkscape:cy="514.28571"
     inkscape:document-units="px"
     inkscape:current-layer="layer1"
     showgrid="false"
     inkscape:window-width="1680"
     inkscape:window-height="995"
     inkscape:window-x="0"
     inkscape:window-y="0"
     inkscape:window-maximized="1" />
  <metadata
     id="metadata7">
    <rdf:RDF>
      <cc:Work
         rdf:about="">
        <dc:format>image/svg+xml</dc:format>
        <dc:type
           rdf:resource="http://purl.org/dc/dcmitype/StillImage" />
        <dc:title></dc:title>
      </cc:Work>
    </rdf:RDF>
  </metadata>
  <g
     inkscape:label="Layer 1"
     inkscape:groupmode="layer"
     id="layer1">
    <path
       sodipodi:type="arc"
       id="big"
       sodipodi:cx="367.14285"
       sodipodi:cy="333.79074"
       sodipodi:rx="132.85715"
       sodipodi:ry="115.71429"
       d="m 500,333.79074 a 132.85715,115.71429 0 1 1 -265.71429,0 132.85715,115.71429 0 1 1 265.71429,0 z"
       style="fill:none;stroke:#000000;stroke-width:2.0999999;stroke-miterlimit:4;stroke-opacity:1;stroke-dasharray:none"
       transform="matrix(0.80424543,0,0,0.80424543,45.656955,42.48392)"
       inkscape:label="#path2985" />
    <path
       sodipodi:type="arc"
       style="fill:none;stroke:#000000;stroke-width:2.0999999;stroke-miterlimit:4;stroke-opacity:1;stroke-dasharray:none"
       id="small"
       sodipodi:cx="404.28571"
       sodipodi:cy="765.2193"
       sodipodi:rx="58.57143"
       sodipodi:ry="58.57143"
       d="m 462.85714,765.2193 a 58.57143,58.57143 0 1 1 -117.14286,0 58.57143,58.57143 0 1 1 117.14286,0 z"
       transform="matrix(0.56870733,0,0,0.56870733,37.222609,150.03348)"
       inkscape:label="#path3755">
       <animateMotion dur="6s" repeatCount="indefinite" rotate="0" >
       <mpath xlink:href="#big"/>
    </animateMotion>
    </path>
  </g>
</svg>


Why does the small ellipse not follow the path of the larger one?