Errors thrown when using version 2.9.56

Hi,
We have encountered following errors when trying to upgrade to the latest Flexmonster-version. Same errors occur when trying to replicate it on a fresh react-project as below.
Commands used:

1. npx create-react-app xxxx
2. added to package.json: "flexmonster": "2.9.56"
3. npm install
4. npm start

With the following App.js:

import "./App.css";
import Flexmonster from "flexmonster";

function App() {
  return (
    <div className="App">
      <div id="pivotContainer">The component will appear here</div>
      <button
        onClick={() =>
          new Flexmonster({
            // container is the id of the <div> created in step 2.2
            container: "pivotContainer",
            componentFolder: "node_modules/flexmonster/",
            toolbar: true,
          })
        }
      >
        Make monster
      </button>
    </div>
  );
}

export default App;

After startup, it shows the following messages in console:
 
WARNING in ./node_modules/flexmonster/flexmonster.full.js 67464:4-36
Module not found: Error: Can't resolve 'worker_threads' in 'C:\Users\.....\node_modules\flexmonster'
 
WARNING in ./node_modules/flexmonster/flexmonster.full.js
Module Warning (from ./node_modules/source-map-loader/dist/cjs.js):
Failed to parse source map from 'C:\Users\...\node_modules\flexmonster\jspdf.umd.min.js.map' file: Error: ENOENT: no such file or directory, open 'C:\Users\...\node_modules\flexmonster\jspdf.umd.min.js.map'
 
webpack compiled with 2 warnings
 
On previous versions (2.9.55 and lower) there are no similar errors