<xs:complexType name="Choice_Narrative_Code_Narrative_45_Type">
<xs:complexContent>
<xs:extension base="ChoiceDataType">
<xs:choice>
<xs:sequence>
<xs:annotation>
<xs:documentation source="Name" xml:lang="EN">Narrative1</xs:documentation>
</xs:annotation>
<xs:element name="Narrative1" type="Text_Unlimited_Type">
<xs:annotation>
<xs:appinfo>
<info:SepPrefix value="//"/>
</xs:appinfo>
<xs:documentation source="Name" xml:lang="EN">Narrative1</xs:documentation>
</xs:annotation>
</xs:element>
</xs:sequence>
<xs:sequence>
<xs:annotation>
<xs:documentation source="Name" xml:lang="EN">Code - Narrative2</xs:documentation>
</xs:annotation>
<xs:element name="Code" type="Text_FIN_8c_Type">
<xs:annotation>
<xs:appinfo>
<info:SepPrefix value="/"/>
<info:SepSuffix value="/"/>
</xs:appinfo>
<xs:documentation source="Name" xml:lang="EN">Code</xs:documentation>
</xs:annotation>
</xs:element>
<xs:element name="Narrative2" type="Text_Unlimited_1_Type" minOccurs="0">
<xs:annotation>
<xs:documentation source="Name" xml:lang="EN">Narrative2</xs:documentation>
</xs:annotation>
</xs:element>
</xs:sequence>
</xs:choice>
</xs:extension>
</xs:complexContent>
</xs:complexType>
<xs:complexType name="F72_106_Narrative_Type">
<xs:complexContent>
<xs:extension base="ComplexDataType">
<xs:sequence>
<xs:annotation>
<xs:appinfo>
<info:Separator value="
"/>
</xs:appinfo>
<xs:documentation source="Name" xml:lang="EN">Line 1 - Lines 2-6</xs:documentation>
</xs:annotation>
<xs:element name="Line1" type="Complex_Code_Narrative_54_Type">
<xs:annotation>
<xs:documentation source="Name" xml:lang="EN">Line 1</xs:documentation>
</xs:annotation>
</xs:element>
<xs:element name="Lines2to6" type="Choice_Narrative_Code_Narrative_45_Type" minOccurs="0" maxOccurs="5">
<xs:annotation>
<xs:documentation source="Name" xml:lang="EN">Lines 2-6</xs:documentation>
</xs:annotation>
</xs:element>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
A 'choice' element type is not supported in older versions of Mendix. I think this is supported in version 5.14 and later. As Reinout suggested, upgrading might solve your problem.
I'm no great expert at XSDs, but at first glance two things jump out at me: