Not answering your question directly, but the RenderX XEP documentation on their support for SVG, is here:
http://www.renderx.com/reference.html#SVGYou could use that to figure out if the SVG files created by a specific tool will work, or to limit the output created by your current tool if possible.
Perhaps you could send RenderX some samples that don't work so they can attempt to improve support for SVG.
An alternative would be to save the SVG images as a different image type (if your software allows for that) that can be embedded into a PDF.