Flutter This AdWidget is already in the Widget tree

Question

After trying out the examples in other posts I am still stumped by this error. I have a list of 50 items and am showing an ad every 10. The first ad loads fine but others do not.

• I have 5 different ad IDs for Native ads to test for that
• I have wrapped the AdWidget in a StatefulBuilder (inside a generated list)
• I have even made a list of AdWidget calling each one only once

This is called for every 10th item in the list (an image is called otherwise)

return StatefulBuilder(builder: (context, setState) {
  return Card(
    shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(0)),
    clipBehavior: Clip.antiAliasWithSaveLayer,
      child: Center(
        child: isAdLoaded?SizedBox(
          height: MediaQuery.of(context).size.width,
            width: MediaQuery.of(context).size.width,
            child: _adWidget[_cardData[index]],
        ):Column(
          mainAxisSize: MainAxisSize.min,
            children: const [
              Icon(
                Icons.help,
                size: 64,
              ),
            Text(
              'There should have been an ad here but something went wrong\nPlease ignore and pardon the inconvenience',
              textAlign: TextAlign.center,
          )
        ],
      ),
    ),
  );
});

This is also called at start in the initState (5 times)

void loadNativeAd(int d) {
    _ad.add(
      NativeAd(
        adUnitId: adList[d],
        factoryId: 'listTileMedium',
        listener: NativeAdListener(
            onAdLoaded: (ad) {
              setState(() {
                isAdLoaded = true;
              });
            },
            onAdFailedToLoad: (ad, error) {
              ad.dispose();
            }
        ),
        request: const AdRequest(),
      ),
    );
    _ad[d].load();

    _adWidget.add(
      AdWidget(
        ad: _ad[d],
      ),
    );
  }