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)



this.setModificationDate(parentItem.get("M"));
      this.data.modificationDate = this.modificationDate;
    }
    if (!parentItem.has("C")) {
      
      this.data.color = null;
    } else {
      this.setColor(parentItem.getArray("C"));
      this.data.color = this.color;
    }
    
    
    
    if (!this.viewable) {
      const parentFlags = parentItem.get("F");
      if (this._isViewable(parentFlags)) {
        this.setFlags(parentFlags);
      }
    }
    this.data.title = stringToPDFString(parentItem.get("T") || "");
    this.data.contents = stringToPDFString(parentItem.get("Contents") || "");
  }
}
class FreeTextAnnotation extends MarkupAnnotation {
  constructor(parameters) {
    super(parameters);
    this.data.annotationType = AnnotationType.FREETEXT;
  }
}
class LineAnnotation extends MarkupAnnotation {