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)



fillAlpha,
        pointsCallback: (buffer, points) => {
          const x0 = points[0].x + this.borderStyle.width / 2;
          const y0 = points[0].y - this.borderStyle.width / 2;
          const x1 = points[3].x - this.borderStyle.width / 2;
          const y1 = points[3].y + this.borderStyle.width / 2;
          const xMid = x0 + (x1 - x0) / 2;
          const yMid = y0 + (y1 - y0) / 2;
          const xOffset = ((x1 - x0) / 2) * controlPointsDistance;
          const yOffset = ((y1 - y0) / 2) * controlPointsDistance;
          buffer.push(
            `${xMid} ${y1} m`,
            `${xMid + xOffset} ${y1} ${x1} ${yMid + yOffset} ${x1} ${yMid} c`,
            `${x1} ${yMid - yOffset} ${xMid + xOffset} ${y0} ${xMid} ${y0} c`,
            `${xMid - xOffset} ${y0} ${x0} ${yMid - yOffset} ${x0} ${yMid} c`,
            `${x0} ${yMid + yOffset} ${xMid - xOffset} ${y1} ${xMid} ${y1} c`,
            "h"
          );
          if (fillColor) {
            buffer.push("B");
          } else {
            buffer.push("S");
          }
          return [points[0].x, points[1].x, points[3].y, points[1].y];
        },
      });
    }
  }
}
class PolylineAnnotation extends MarkupAnnotation {