See issue description in parent issue.
Basically, we should never send the mimeType when saving a BinaryFile field, it's up to server to correctly compute this value from what it receives.
Most likely the same happens with Image and Media fields as well.

Steps to reproduce:

• Create a content having a File field type.
• Add a file (let say an image file)
• Publish the content
• Edit the content
• Click on replace this file and select an different type of file (let say an audio file)
• Open the dev tool console of your favorite browser to check the request that will be sent
• Click on save.
• Check the PATCH request, for the image fieldtype the mime type will still be the previous one (so an image in our example).