With POST-Queries all "Any" and "All"-Predicates should use OData syntax for member access!
In OData, when used in JSON Syntax, member access in "any"/"all" predicates is not allowed to use "." (dot). Instead "/" should be used - otherwise the following exception will be raised:
Microsoft.Data.OData.ODataException ist aufgetreten.
HResult=-2146233079
Message=The child type 'ToOrderKind.Name' in a cast was not an entity type. Casts can only be performed on entity types.
Source=Microsoft.Data.OData
StackTrace:
bei Microsoft.Data.OData.Query.DottedIdentifierBinder.BindDottedIdentifier(DottedIdentifierToken dottedIdentifierToken, BindingState state)
InnerException:
Breeze-Queries with POST-Method (which use JSON-Syntax) should replace "." with "/" in all "Any" and "All"-Predicates automatically. At the moment we have to do this manually.

We will not be supporting OData in our .NET Core libraries. We determined that OData community was declining and our json encoded urls provided more complete support for the current breeze query capabilities as well as the ability to extend this support in the future.