I created a pdf for https://github.com/mozilla/pdf.js/pull/14023:
[same_fields(1).pdf](https://github.com/mozilla/pdf.js/files/7168340/same_fields.1.pdf)
The 3 checkboxes have the same name (`Check Box2`) and have the same values (`Off` and `Yes`).
In pdf.js, these checkboxes behave like radio buttons in the same group (which is wrong) because of:
https://github.com/mozilla/pdf.js/commit/1fcffe80349a98378262c8a16f7b50ff34c3fe82
Since they've the same values they must be synced: if one is checked (resp. unchecked) then all others are checked (resp. unchecked).
selectElement.multiple = true;
          },
          remove(event) {
            const options = selectElement.options;
            const index = event.detail.remove;
            options[index].selected = false;
            selectElement.remove(index);
            if (options.length > 0) {
              const i = Array.prototype.findIndex.call(
                options,
                option => option.selected
              );
              if (i === -1) {
                options[0].selected = true;
              }
            }
            storage.setValue(id, {
              value: getValue(event,  true),
              items: getItems(event),
            });
          },
          clear(event) {