XSLT mapping to correct XML format in Input file

Question

I am checking on the possibility of correcting the input XML file syntax with XSLT 1.0 mapping, but not able to find any relevant blogs, is this even possible ?

Input is a combination multiple files, below are the sample input and outputs, Please suggest.

Input

<?xml version="1.0" encoding="UTF-8"?>
<HEADER>
    <CHILD BEGIN="1">
        <RECORD SEGMENT="1">
            <FIELD1>value1</FIELD1>
            <FIELD2>2</FIELD2>      
        </RECORD>       
    </CHILD>
</HEADER>
<?xml version="1.0" encoding="UTF-8"?>
<HEADER>
    <CHILD BEGIN="1">
        <RECORD SEGMENT="1">
            <FIELD1>value2</FIELD1>
            <FIELD2>3</FIELD2>

        </RECORD>   
    </CHILD>
</HEADER>

output

<?xml version="1.0" encoding="UTF-8"?>
<HEADER>
    <CHILD BEGIN="1">
        <RECORD SEGMENT="1">
            <FIELD1>value1</FIELD1>
            <FIELD2>2</FIELD2>      
        </RECORD>       
    </CHILD>

    <CHILD BEGIN="1">
        <RECORD SEGMENT="1">
            <FIELD1>value2</FIELD1>
            <FIELD2>3</FIELD2>

        </RECORD>   
    </CHILD>
</HEADER>

Answer 1

In XSLT 2/3, as pointed in a comment to the other answer, you could try to process the input as plain text (by using unparsed-text on the input file or by passing its content as a string value/string item to the transformation):

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  version="3.0"
  xmlns:xs="http://www.w3.org/2001/XMLSchema"
  exclude-result-prefixes="#all"
  expand-text="yes">

  <xsl:output method="xml" indent="yes"/>

  <xsl:template match=".[. instance of xs:string]" name="xsl:initial-template">
    
    <xsl:variable name="elements" as="element()*">
      <xsl:for-each-group select="tokenize(., '\r?\n')" group-starting-with=".[starts-with(., '&lt;?xml version')]">
        <xsl:sequence select="(current-group() => tail() => string-join('&#10;') => parse-xml-fragment()) ! *"/>
      </xsl:for-each-group>      
    </xsl:variable>

    <xsl:for-each-group select="$elements" group-by="node-name()">
      <xsl:copy>
        <xsl:copy-of select="@*, current-group()!*"/>
      </xsl:copy>
    </xsl:for-each-group>
    
  </xsl:template>

</xsl:stylesheet>

Online example passing input as string value/string item.