REST Error Response

I’m trying to patch to a UBAQ through a middleware tool, but it’s giving me this error and I’m not sure why:

  <ReasonPhrase>REST API Exception</ReasonPhrase>
  <ErrorMessage>UpdateQuery data error. Unable to deserialize payload.</ErrorMessage>

This is the payload being sent:

  "ShipHead_PackNum": "91343",
  "ShipHead_TrackingNumber": "12345ADGCEEFG"

And here’s it working successfully with the same data in Postman:

Narrowed it down to something to do with the parameter.
I took the parameter out of the query since PackNum is a unique identifier and it seems to work now…