--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.

Are you confusing a variable and a node?

When a variable and a child element share a name, a bare title in the select of xsl:apply-templates, xsl:for-each, xsl:value-of, or xsl:copy-of picks the child, and the variable is silently ignored. Write $title for the variable. Where the variable may hold an atomic value, rename it or spell the child child::title instead.

Incorrect:

<xsl:template match="/">
  <xsl:variable name="title" select="book/title"/>
  <xsl:apply-templates select="title"/>
</xsl:template>

Correct:

<xsl:template match="/">
  <xsl:variable name="title" select="book/title"/>
  <xsl:apply-templates select="$title"/>
</xsl:template>

Only a name opening a path is checked, against a variable in scope that binds its value with select.