using the schema:
<element name="number" xmlns="http://relaxng.org/ns/structure/1.0">
   <attribute name="val">
      <list>
         <oneOrMore>
            <choice>
               <value>1</value>
               <value>2</value>
               <value>3</value>
            </choice>
         </oneOrMore>
      </list>
   </attribute>
   <text/>
</element>

This document fails validation (correct):
<number val="a 1 b 2 c 3" />

This document passes validation (wrong):
<number val="1 a 2 b 3 c" />

In xmlRelaxNGValidateValue, the type XML_RELAXNG_CHOICE calls
xmlRelaxNGValidateValue and type is XML_RELAXNG_VALUE. After validating it calls
xmlRelaxNGNextValue. When call returns to the XML_RELAXNG_CHOICE block,
xmlRelaxNGNextValue is called again, which skips the next value in the list.