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)



constructor(params) {
    const dict = params.dict;
    this.setContents(dict.get("Contents"));
    this.setModificationDate(dict.get("M"));
    this.setFlags(dict.get("F"));
    this.setRectangle(dict.getArray("Rect"));
    this.setColor(dict.getArray("C"));
    this.setBorderStyle(dict);
    this.setAppearance(dict);
    this._streams = [];
    if (this.appearance) {
      this._streams.push(this.appearance);
    }
    
    this.data = {
      annotationFlags: this.flags,
      borderStyle: this.borderStyle,
      color: this.color,
      contents: this.contents,
      hasAppearance: !!this.appearance,
      id: params.id,
      modificationDate: this.modificationDate,
      rect: this.rectangle,
      subtype: params.subtype,
    };