Can you confirm if your modelParams follows the requirements mentioned here:

• modelParameters (optional): A struct field that contains chat, completion and embedding model parameters for serving foundation models or external models. These model parameters must be constant parameters and not data dependent. When these model parameters are not specified or set to null the default value is used. With the exception of temperature which has a default value of 0.0, the default values for these model parameters are the same as those listed in Foundation model REST API reference.