The schema processor may report a schema to be in violation of the Element Declarations Consistent rule when it is actually valid.
The problem occurs when a content model contains two element particles A and B, and B is in the substitution group of A, and B has a type that is a restriction of the type of A. Saxon is checking, in effect, that A and B have the same type, whereas what is actually required is that the B that appears in the content model has the same type as the B that appears in the substitution group of A (which will automatically be true, of course, if they are both references to the same global element declaration).
The problem is caused by ambiguous wording of the EDC constraint in the XSD 1.0 specification. XSD 1.1 has made a slight alteration to the wording which removes this ambiguity.
A patch will be raised in the Saxon-SA source repository, and will become available to users in the next maintenance release.
The problem is revealed by running
java com.saxonica.Validate -xsd:http://schemas.opengis.net/ows/1.1.0/owsAll.xsd