This problem applies to all the documents that I have ever opened.

Configuration:
- Web browser and its version: Google Chrome 83.0.4103.61 , also Firefox 76.0.1
- Operating system and its version: Win 7 x64
- PDF.js version: 2.3.164 version of extension
- Is a browser extension: yes

Steps to reproduce the problem:
1. Select any "Spreads" mode of view. Or "No spreads", but wrapped scrolling mode - doesn't matter. 
2. Select "Page Fit" zoom mode. We should get several pages per screen
3. Try to scroll document by any of keys: Page Down, n, j, Space Bar

I expect to see the next group of pages (for example, if there are 5 pages on the screen, I expect to see the next 5 pages)

What went wrong? Scrolling goes one page at a time, so if I have 5 pages on the screen, nothing happens when I pressed Page Down 5 times . For the 6th time I finally see the next group of pages.

Just for example: Adobe Reader scrolls properly in two-page mode, 2 pages at once. 

P.S. Sorry for my English, I hope I correctly stated the essence of the problem
this._cancelIdleCallbacks();
    promises.push(this._destroyScriptingInstance());
    this.pdfSidebar.reset();
    this.pdfOutlineViewer.reset();
    this.pdfAttachmentViewer.reset();
    this.pdfLayerViewer.reset();
    if (this.pdfHistory) {
      this.pdfHistory.reset();
    }
    if (this.findBar) {
      this.findBar.reset();
    }
    this.toolbar.reset();
    this.secondaryToolbar.reset();
    if (typeof PDFBug !== "undefined") {
      PDFBug.cleanup();
    }
    await Promise.all(promises);
    return undefined;
  },
  /**
   * Opens PDF document specified by URL or array with additional arguments.
   * @param {string|TypedArray|ArrayBuffer} file - PDF location or binary data.
   * @param {Object} [args] - Additional arguments for the getDocument call,
   *                          e.g. HTTP headers ('httpHeaders') or alternative
   *                          data transport ('range').
   * @returns {Promise} - Returns the promise, which is resolved when document
   *                      is opened.
   */
  async open(file, args) {