Problems with footnotes in term of varlistentry

[Georges Schmitz <georges.schmitz@arcor.de>]

It happened that I used the following construct (without much thinking 
about the consequences):

  <variablelist>
    <varlistentry id="btn-down">
      <term><guibutton>Runter</guibutton><footnote>
      <para>Hitting <xref linkend="btn-down"/> blabla ... </para>
      </footnote></term>

      <listitem>
        <para>blabla </para>
      </listitem>
    </varlistentry>
  </variablelist>

  ... (several pages between)

  <para>As against using <xref linkend="btn-down"/> blabla ... </para>

[A]
OK, the use of the 1st xref is a clear mistake caused by me. All 
transformers crashed when processing the FO stylesheets (xalan produces 
a stack overflow, xsltproc did never come back, with saxon I don't know 
anymore, what the console said) and it was very hard to find the 
problem, because the document validates and after crashing, you don't 
get a clue, what's wrong, not even by looking into the incomplete FO 
fragment, that was produced by xalan. What astonished me: the HTML 
stylesheets don't seem to have problems with this construct.

Is it possible to modify the stylesheet in that way, that it can 
recognize running into an infinite loop caused by a circular reference? 
Or is it even possible to check this in RNG (don't know much about it, 
only that it can express stricter checks than DTD).

[B]
The generated text for the second xref contains a footnotemark. Can this 
be avoided? If the reference appears on a different side than the term, 
even the footnote text itself is displayed a second time.

Thanks,
Georges

--
Using DTD 4.4 and stylesheet version1.70.0