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
const errorWrapper = this.appConfig.errorWrapper.container;
    errorWrapper.setAttribute("hidden", "true");
    if (!this.pdfLoadingTask) {
      return undefined;
    }
    const promises = [];
    promises.push(this.pdfLoadingTask.destroy());
    this.pdfLoadingTask = null;
    if (this.pdfDocument) {
      this.pdfDocument = null;
      this.pdfThumbnailViewer.setDocument(null);
      this.pdfViewer.setDocument(null);
      this.pdfLinkService.setDocument(null);
      this.pdfDocumentProperties.setDocument(null);
    }
    webViewerResetPermissions();
    this.store = null;
    this.isInitialViewSet = false;
    this.downloadComplete = false;
    this.url = "";
    this.baseUrl = "";
    this.documentInfo = null;
    this.metadata = null;
    this._contentDispositionFilename = null;
    this._contentLength = null;
    this.triggerDelayedFallback = null;
    this._saveInProgress = false;