--fix-suggestions rewrites this one, and a plain --fix leaves it alone: the correction changes what the stylesheet does, or is one of several the check would accept.

Redundant import

Importing one module twice puts it at two precedence levels, so a reader cannot tell which copy of a template wins or what xsl:apply-imports reaches next. Including it twice defines every template in it twice at one precedence. Importing and also including it is worse: the included copy shadows the imported one, and the stylesheet's own templates now collide with it at equal precedence. Keep one reference, chosen with the stylesheet's overriding in view.

Incorrect:

<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:import href="common.xsl"/>
  <xsl:include href="common.xsl"/>
</xsl:stylesheet>

Correct:

<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:include href="common.xsl"/>
</xsl:stylesheet>

Two hrefs that resolve to the same file, such as lib/util.xsl and ./lib/util.xsl, count as one module.