Hi @philschmid ,  I got solution from another related post under your help as well :
How are the inputs tokenized when model deployment? - Amazon SageMaker - Hugging Face Forums 2
After I switch to another model and remodify the input json file format like this:
{“inputs”: “long sentence 2”, “parameters”: {“trucation”: true}},  the new model works well for me ( as long as it has ‘max_length’ attribute in tokenizer config file.)