Just throwing this out there. When the ETT site was still up, I had run into a case where the Validator wasn't checking everything it should. I discovered that my XML had some places where a <code> contained an empty value instead of a nullFlavor. Like this
<code code="" codeSystem="2.16.840.1.113883.6.1" codeSystemName="LOINC" displayName=""/>
Once I fixed those, then the Validator was able to check all 3 categories