/new_data/feedback TypeError: the JSON object must be str, bytes or bytearray, not dict

Start in flask_api.py at save_feedback around line 239 and inspect how request.get_json() is passed to json.loads(). Reproduce the POST to /new_data/feedback with the payload that triggered the stack trace; done means valid JSON requests no longer raise this TypeError or return HTTP 500.

Stacktrace

May 28 09:44:03 AM  10.100.0.191 - - [28/May/2020:16:44:03 +0000] "GET / HTTP/1.1" 200 37 "-" "Render/1.0"
May 28 09:44:08 AM  10.104.30.4 - - [28/May/2020:16:44:08 +0000] "OPTIONS /new_data/feedback HTTP/1.1" 200 0 "https://nimbus.calpolycsai.com/" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.138 Safari/537.36"
May 28 09:44:08 AM  [2020-05-28 16:44:08,122] ERROR in app: Exception on /new_data/feedback [POST]
May 28 09:44:08 AM  Traceback (most recent call last):
  File "/opt/render/project/src/.venv/lib/python3.7/site-packages/flask/app.py", line 2446, in wsgi_app
    response = self.full_dispatch_request()
  File "/opt/render/project/src/.venv/lib/python3.7/site-packages/flask/app.py", line 1951, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/opt/render/project/src/.venv/lib/python3.7/site-packages/flask_cors/extension.py", line 161, in wrapped_function
    return cors_after_request(app.make_response(f(*args, **kwargs)))
  File "/opt/render/project/src/.venv/lib/python3.7/site-packages/flask/app.py", line 1820, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/opt/render/project/src/.venv/lib/python3.7/site-packages/flask/_compat.py", line 39, in reraise
    raise value
  File "/opt/render/project/src/.venv/lib/python3.7/site-packages/flask/app.py", line 1949, in full_dispatch_request
    rv = self.dispatch_request()
  File "/opt/render/project/src/.venv/lib/python3.7/site-packages/flask/app.py", line 1935, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/opt/render/project/src/flask_api.py", line 239, in save_feedback
    data = json.loads(request.get_json())
  File "/usr/local/lib/python3.7/json/__init__.py", line 341, in loads
    raise TypeError(f'the JSON object must be str, bytes or bytearray, '
TypeError: the JSON object must be str, bytes or bytearray, not dict
May 28 09:44:08 AM  10.104.30.4 - - [28/May/2020:16:44:08 +0000] "POST /new_data/feedback HTTP/1.1" 500 290 "https://nimbus.calpolycsai.com/" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.138 Safari/537.36"