Online form gives 404 on certain schema (it can't handle?)

Hi,

I am trying to use the online validator
https://www.softwarebytes.org/xmlvalidation/ to perform XSD 1.1
validation with Xerces but on a certain schema I only get a 404 when
submitting the form; here is the instance XML

<root>
 =C2=A0 <value>axyughji</value>
 =C2=A0 <value>axgh</value>
 =C2=A0 <value>agh</value>
 =C2=A0 <value>h</value>
 =C2=A0 <value>agHXU</value>
 =C2=A0 <value>axXgh</value>
 =C2=A0 <value>axxhu</value>
 =C2=A0 <value>AXYUGHJIA</value>
 =C2=A0 <value>ATXYUGHM</value>
</root>

and here is the schema:

<xs:schema xmlns:xs=3D"http://www.w3.org/2001/XMLSchema">

 =C2=A0 <xs:element name=3D"root">
 =C2=A0=C2=A0=C2=A0 <xs:complexType>
 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 <xs:sequence>
 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 <xs:element name=3D"value" typ=
e=3D"value-type" maxOccurs=3D"unbounded"/>
 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 </xs:sequence>
 =C2=A0=C2=A0=C2=A0 </xs:complexType>
 =C2=A0 </xs:element>

 =C2=A0 <xs:simpleType name=3D"value-type">
 =C2=A0=C2=A0=C2=A0 <xs:restriction base=3D"xs:string">
 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 <xs:minLength value=3D"0"/>
 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 <xs:maxLength value=3D"8"/>
 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 <xs:assertion test=3D"matches(=
$value, '^[axyughji]{0,8}$', 'i')
and count(distinct-values(string-to-codepoints(lower-case($value)))) eq
string-length($value)"/>
 =C2=A0=C2=A0=C2=A0 </xs:restriction>
 =C2=A0 </xs:simpleType>

</xs:schema>

What do you think, is that a bug in the validator form, in the
underlying Xerces parser or in my schema (runs fine through Saxon EE
though)?