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._setScale(this._currentScaleValue, true);
    }
    this._setCurrentPageNumber(pageNumber,  true);
    this.update();
  }
  initializeScriptingEvents() {
    if (!this.enableScripting || this._pageOpenPendingSet) {
      return;
    }
    const eventBus = this.eventBus,
      pageOpenPendingSet = (this._pageOpenPendingSet = new Set()),
      scriptingEvents = (this._scriptingEvents ||= Object.create(null));
    const dispatchPageClose = pageNumber => {
      if (pageOpenPendingSet.has(pageNumber)) {
        return; 
      }
      eventBus.dispatch("pageclose", { source: this, pageNumber });
    };
    const dispatchPageOpen = pageNumber => {
      const pageView = this._pages[pageNumber - 1];
      if (pageView?.renderingState === RenderingStates.FINISHED) {
        pageOpenPendingSet.delete(pageNumber);
        eventBus.dispatch("pageopen", {
          source: this,
          pageNumber,
          actionsPromise: pageView.pdfPage?.getJSActions(),
        });
      } else {
        pageOpenPendingSet.add(pageNumber);
      }