How do I update file in a model in strapi via API?

I am able to upload many files using the below approach


    const formData = new FormData();
    inputs.files.forEach(({ file }) => {
      formData.append(`files`, file, file.name);
    });
    const data = {
      ...someData
    };
    formData.append("data", JSON.stringify(data));

Looking at your request it is difficult for me to say but have you tried something like:
formData.append('files', fileStream, 'myfile.jpg');