Как обнаружить в чем ошибка загрузки данных с сервера (React/Redux/thunk)?

import React from "react";
import { connect } from "react-redux";

import { commentSelectorFactory } from "../selectors";

const Comment = ({ comment }) => (
  <div>
    <h5>{ comment.user }</h5>
    { comment.text }
  </div>
);

export default connect(
  () => {
    const commentSelector = commentSelectorFactory();

    return (state, ownProps) => {
      return {
        comment: commentSelector(state, ownProps) // Запрос комментария из селектора
      };
    };
  }
)(Comment);

export const commentSelectorFactory = () => createSelector(commentsGetter, idGetter, (comments, id) => {
  return comments.getIn(["entities", id]); // Получить комментарий по id
});

import { arrToMap } from "../helpers";
import { OrderedMap, Record } from "immutable";

const CommentRecord = Record({
  id: null,
  text: "",
  user: ""
});

const ReducerState = Record({
  entities: new OrderedMap({})
});

const defaultState = new ReducerState();

export default (commentsState = defaultState, action) => {
  switch (action.type) {
    case "ADD_COMMENT": {
      return commentsState.setIn(["entities", action.randomId], new CommentRecord({ ...action.payload.comment, id: action.ramdomId }));
    }

    case "LOAD_ARTICLE_COMMENTS_SUCCESS": { // В middleware добавляется _SUCCESS
      return commentsState.mergeIn(['entities'], arrToMap(action.response, CommentRecord));
    }

    default: {
      return commentsState;
    }
  }
};

import { OrderedMap } from "immutable";

export function arrToMap(arr, RecordModel) {
    return arr.reduce((acc, el) => acc.set(el.id, RecordModel ? new RecordModel(el) : el), new OrderedMap({}))
}

export function loadArticleComments(articleId) {
    console.log("Action creator loadArticleComments: ");

    return {
        type: "LOAD_ARTICLE_COMMENTS",
        payload: { articleId },
        callAPI: `/api/comment?article=${articleId}`
    }
}

export default store => next => action => {
  const { callAPI, type, ...rest } = action;

  if (!callAPI) {
    return next(action);
  }

  next({
    ...rest,
    type: type + "_START"
  });

  fetch(callAPI)
    .then(res => res.json())
    .then(response => next({
      ...rest,
      type: type + "_SUCCESS",
      response
    })
  );
};

import React from "react";
import { connect } from "react-redux";

import { loadArticleComments } from "../AC";

import "./CommentList.css";

import Comment from "./Comment";
import CommentForm from "./CommentForm";

import toggleOpen from "../decorators/toggleOpen";

class CommentList extends React.Component {
  componentWillReceiveProps({ isOpen, article, loadArticleComments }) {
      if (!this.props.isOpen && isOpen && !article.commentsLoading && !article.commentsLoaded) {
          loadArticleComments(article.id)
      }
  }

  getCommentsBody = () => {
    const { article: { comments = [], id } } = this.props;

    if (!comments) {
      return (
        <div>
          <div>empty</div>
          <CommentForm articleId = { id } />
        </div>
      );
    }

    return (
      <div className="comment-list">
        <ul className="list-group">
          {
            comments.map(id => (
              <li className="list-group-item" key = { id }>
                <Comment id = { id } /> // Рендер комментария
              </li>
            ))
          }
        </ul>
        <CommentForm articleId = { id } />
      </div>
    );
  }

  render() {
    return (
      <div>
        <button className="btn btn-dark" onClick = { this.props.handleToggle }>{ this.props.isOpen ? "close comments" : "open comments" }</button>
        { this.props.isOpen && this.getCommentsBody() }
      </div>
    );
  }
}

export default connect(null, {
  loadArticleComments
})(toggleOpen(CommentList));