Attach (recommended) or Link to PDF file here:
https://s3.eu-west-1.amazonaws.com/scai-dev.website.com/tmp/8ab8b56a-fa91-11eb-8d74-0242ac110004.pdf

Hi,
Please see an incorrect canvas rendering for the following document - page 9 specifically. It reproduces on https://mozilla.github.io/pdf.js/web/viewer.html (tried with Chrome). Other pages in this document look pretty much the same but the problem is on page 9 only.

Original screenshot:
![image](https://user-images.githubusercontent.com/23075641/129066656-7bb2fb56-2b88-4f40-8e67-b95bdeb9e521.png)


PDF JS:

![image](https://user-images.githubusercontent.com/23075641/129066734-56503a5c-413c-49c1-9e1c-470da3a642ed.png)

scaleX = drawnWidth / MAX_GROUP_SIZE;
      drawnWidth = MAX_GROUP_SIZE;
    }
    if (drawnHeight > MAX_GROUP_SIZE) {
      scaleY = drawnHeight / MAX_GROUP_SIZE;
      drawnHeight = MAX_GROUP_SIZE;
    }
    let cacheId = "groupAt" + this.groupLevel;
    if (group.smask) {
      
      cacheId += "_smask_" + (this.smaskCounter++ % 2);
    }
    const scratchCanvas = this.cachedCanvases.getCanvas(
      cacheId,
      drawnWidth,
      drawnHeight,
      true
    );
    const groupCtx = scratchCanvas.context;
    
    
    groupCtx.scale(1 / scaleX, 1 / scaleY);
    groupCtx.translate(-offsetX, -offsetY);
    groupCtx.transform.apply(groupCtx, currentTransform);
    if (group.smask) {
      
      this.smaskStack.push({
        canvas: scratchCanvas.canvas,
        context: groupCtx,
        offsetX,