Word file used: 
[Formular_T.docx](https://github.com/mozilla/pdf.js/files/6907859/Formular_T.docx)

PDFs generated:
PDF 1: [Formular_T_default.pdf](https://github.com/mozilla/pdf.js/files/6907771/Formular_T_default.pdf)
PDF 2: [Formular_T_changed.pdf](https://github.com/mozilla/pdf.js/files/6907772/Formular_T_changed.pdf)

- PDF.js version: v2.9.359

Steps to reproduce the problem:
1. Create Word Document with Checkbox and check it.
2. Convert Word document to PDF using **Aspose.pdf** (for .net)

3. Extra: Change value of second Checkbox  in PDF 1 and save the file (PDF 2). The new File will show both Checkboxes checked in other browser, but only the newly checked one in PDF.js

Expected:
Checkbox is checked (pdf viewer from adobe/Chrome Version 92.0.4515.107 64-bit)
![image](https://user-images.githubusercontent.com/76941221/127659557-42be1cca-3c90-49b8-b224-70ee85aa1b30.png)

Result:
Checkbox is not checked (Mozilla Firefox/PDF.js)
![image](https://user-images.githubusercontent.com/76941221/127660064-e3cdc3f9-6887-4ae7-af27-d46cded69029.png)



const bbox = [Infinity, Infinity, -Infinity, -Infinity];
      for (const vertex of this.data.vertices) {
        bbox[0] = Math.min(bbox[0], vertex.x - borderAdjust);
        bbox[1] = Math.min(bbox[1], vertex.y - borderAdjust);
        bbox[2] = Math.max(bbox[2], vertex.x + borderAdjust);
        bbox[3] = Math.max(bbox[3], vertex.y + borderAdjust);
      }
      if (!Util.intersect(this.rectangle, bbox)) {
        this.rectangle = bbox;
      }
      this._setDefaultAppearance({
        xref: parameters.xref,
        extra: `${borderWidth} w`,
        strokeColor,
        strokeAlpha,
        pointsCallback: (buffer, points) => {
          const vertices = this.data.vertices;
          for (let i = 0, ii = vertices.length; i < ii; i++) {
            buffer.push(
              `${vertices[i].x} ${vertices[i].y} ${i === 0 ? "m" : "l"}`
            );
          }
          buffer.push("S");
          return [points[0].x, points[1].x, points[3].y, points[1].y];
        },
      });
    }
  }
}
class PolygonAnnotation extends PolylineAnnotation {