Web Service: some input parameters remain empty

Question

VBScript

Not the first day trying to understand why this can happen. The problem itself has already been localized, but the cause of its origin has not been found and is not clear.
Description of the problem:
The web method has optional fields that are filled in by default, if a value is passed to them from external clients, then the parameters are filled. But if an attempt is made to call a web service in a client written in VBScript via oXMLHTTP, then parameters that have default values ​​are not transmitted and remain with default values, although all fields are present and filled in the incoming SOAP request.
But what is strange, some parameters are still filled. This parameter is the last one in the list of method parameters.
Part of the method parameters is of type int, the other part is string. If I translate all parameters into string, then in this case all parameters are filled.
The question is why this can happen exactly when working with VBScript.