XSD validator (ex. VSCode XML extension from RedHat) will flag lines 191-196 as errors.

"code": "cos-all-limited.2",
"severity": 8,
"message": "cos-all-limited.2: The {max occurs} of an element in an 'all' model group must be 0 or 1. The value 'unbounded' for element 'configuration' is invalid.",
"source": "xsd",
"startLineNumber": 190,
"startColumn": 11,
"endLineNumber": 190,
"endColumn": 17  

The following changes appear to resolve the issue:

Change line 190 to: <xs:choice maxOccurs="unbounded">

Change line 197 to: </xs:choice>