What is the correct way of allowing uploading of non-text based files?

[SCSR-is-too-short-username]

Basically we have a file upload endpoint that allows uploading on several file types. Some are text based (like json and csv) and some are not (like xlsx). When trying to upload non-text based files I get the following error message:

Traceback (most recent call last):
  File "C:\Users\user\Documents\project\api\node_modules\serverless-offline\dist\lambda\handler-runner\python-runner\invoke.py", line 97, in <module>

    result = handler(input['event'], context)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\user\Documents\project\.venv\Lib\site-packages\mangum\adapter.py", line 82, in __call__

    http_cycle = HTTPCycle(handler.scope, handler.body)

                                          ^^^^^^^^^^^^
  File "C:\Users\user\Documents\project\.venv\Lib\site-packages\mangum\handlers\api_gateway.py", line 83, in body

    return maybe_encode_body(

       ^^^^^^^^^^^^^^^^^^
  File "C:\Users\user\Documents\project\.venv\Lib\site-packages\mangum\handlers\utils.py", line 13, in maybe_encode_body

    body = body.encode()

           ^^^^^^^^^^^^^
UnicodeEncodeError: 'utf-8' codec can't encode character '\udc8f' in position 228: surrogates not allowed

What is the correct way of allowing these files to be also uploaded and not have mangum throw an error? The post request header has Content-Type set to multipart/form-data