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)



if (key !== "Off") {
        this.data.buttonValue = this._decodeFormValue(key);
        break;
      }
    }
    this.checkedAppearance = normalAppearance.get(this.data.buttonValue);
    this.uncheckedAppearance = normalAppearance.get("Off") || null;
    this._streams.push(this.checkedAppearance);
    if (this.uncheckedAppearance) {
      this._streams.push(this.uncheckedAppearance);
    }
    this._fallbackFontDict = this.fallbackFontDict;
  }
  _processPushButton(params) {
    if (
      !params.dict.has("A") &&
      !params.dict.has("AA") &&
      !this.data.alternativeText
    ) {
      warn("Push buttons without action dictionaries are not supported");
      return;
    }
    this.data.isTooltipOnly = !params.dict.has("A") && !params.dict.has("AA");
    Catalog.parseDestDictionary({
      destDict: params.dict,
      resultObj: this.data,
      docBaseUrl: params.pdfManager.docBaseUrl,
    });
  }
  getFieldObject() {