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
if ("nameddest" in params) {
        this.goToDestination(params.nameddest);
      }
    } else {
      
      dest = unescape(hash);
      try {
        dest = JSON.parse(dest);
        if (!Array.isArray(dest)) {
          
          
          dest = dest.toString();
        }
      } catch (ex) {}
      if (typeof dest === "string" || isValidExplicitDestination(dest)) {
        this.goToDestination(dest);
        return;
      }
      console.error(
        `PDFLinkService.setHash: "${unescape(hash)}" is not ` +
          "a valid destination."
      );
    }
  }
  /**
   * @param {string} action
   */
  executeNamedAction(action) {