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 acroFormResources = params.acroForm.get("DR");
    const appearanceResources =
      this.appearance && this.appearance.dict.get("Resources");
    this._fieldResources = {
      localResources,
      acroFormResources,
      appearanceResources,
      mergedResources: Dict.merge({
        xref: params.xref,
        dictArray: [localResources, appearanceResources, acroFormResources],
        mergeSubDicts: true,
      }),
    };
    data.fieldFlags = getInheritableProperty({ dict, key: "Ff" });
    if (!Number.isInteger(data.fieldFlags) || data.fieldFlags < 0) {
      data.fieldFlags = 0;
    }
    data.readOnly = this.hasFieldFlag(AnnotationFieldFlag.READONLY);
    data.hidden = this._hasFlag(data.annotationFlags, AnnotationFlag.HIDDEN);
  }
  /**
   * Decode the given form value.
   *
   * @private
   * @memberof WidgetAnnotation
   * @param {Array<string>|Name|string} formValue - The (possibly encoded)
   *   form value.
   * @returns {Array<string>|string|null}
   */
  _decodeFormValue(formValue) {