That does sound like there is a problem with the destination services. Do you have a wsdl or swagger url? Also please provide a screenshot of your client service and or wsdl/swagger. You can mask the secrets and confidential information, end point url, hostnames etc.
If you want to pass a string value to a primitive type field in remote server, you need to create a document or import the document to IS using swagger or wsdl or something similar (xsd, json schema or something). In the document if you set the field type to be integer/double/etc, integration server will do the necessary conversion. If you don’t do this, and pass the value as it is to the destination, you rely on destination services conversion mechanics. Most backend services does this automatically, but its usually better to stick to the protocol instead of relying on assumptions.
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