Как отправить почтовый запрос с почтальоном, а также сохранить в базе данных Mongo?

Я делаю API генератора вымышленных персонажей. Работает нормально, когда я отправляю запросы через Postman при локальном запуске, но выдает ошибку 500 и время ожидания при запуске через докер. В указанном приложении API фляги:

from flask import Flask, jsonify, request
from flask_restful import Api, Resource
... 
class AddCharacter(Resource):
    def post(self):
...
        p.add_person()
        # saves the character to a mongodb
        p.save_person() #<-- causes a 500 error in postman when run through docker build and docker up
        retJson = {
            "Message": "Character has been created",
            "Status Code": 200
        }
        return jsonify(retJson)

Как я подключаюсь к монго:

db = MongoEngine()

app = Flask(__name__)

app.config['MONGODB_SETTINGS'] = {
    'db': 'projectdb',
    'host': 'localhost',
    'port': 27017


}

with app.app_context():
    db.init_app(app)
    try:
        db_client = db.connection['projectdb']
    except ConnectionFailure as e:
        sys.stderr.write("Could not connect to MongoDB: %s" % e)
    sys.exit(1)

менеджер базы данных:

class DatabaseManager():

    def save_user(self, first_name, last_name, openness, conscientiousness, extraversion,
                  agreeableness, emotional_stability, organization, anxiety,
                  knowledgeableness, sympathy, talkativeness, accommodation,
                  expressiveness, carefulness, depressiveness, gregariousness,
                  altruism, inquisitiveness):
        new_user = User(first_name=first_name, last_name=last_name)
        new_user.save()
        new_personality = Personality(Openness=openness, Conscientiousness=conscientiousness, Extraversion=extraversion,
                                      Agreeableness=agreeableness, EmotionalStability=emotional_stability,
                                      Organization=organization, Anxiety=anxiety,
                                      Knowledgeableness=knowledgeableness, Sympathy=sympathy,
                                      Talkativeness=talkativeness, Accommodation=accommodation,
                                      Expressiveness=expressiveness, Carefulness=carefulness,
                                      Depressiveness=depressiveness, Gregariousness=gregariousness,
                                      Altruism=altruism, Inquisitiveness=inquisitiveness)
        new_profile = Profile(person=new_user, personality=new_personality)
        new_profile.save()

В классе Человек:

def save_person(self):
    dm.save_user(first_name=self.first_name, last_name=self.last_name, openness=aff.Openness,
                 conscientiousness=aff.Conscientiousness, extraversion=aff.Extraversion,
                 agreeableness=aff.Agreeableness, emotional_stability=aff.EmotionalStability,
                 organization=aff.Organization, anxiety=aff.Anxiety,
                 knowledgeableness=aff.Knowledgeableness, sympathy=aff.Sympathy, talkativeness=aff.Talkativeness,
                 accommodation=aff.Accommodation,
                 expressiveness=aff.Expressiveness, carefulness=aff.Carefulness, depressiveness=aff.Depressiveness,
                 gregariousness=aff.Gregariousness,
                 altruism=aff.Altruism, inquisitiveness=aff.Inquisitiveness)

файловая структура, Dockerfile, требования.txt, образы файлов .yml. Я запускаю докер с sudo docker-compose build, а затем sudo docker-compose up