Double Tap in Textformfield not possible, when TextFormField is inside a Component

I am using a TextFormfield inside a StatefulWidget which is used in another StatefulWidget.

My problem is, that the doubletap in this Textformfield is not possible. If I try to doubletap in a TextFormField which I use directly inside the StatefulWidget it works flawless.

    BankverbindungFormField(.  <- doesn't work
        bankverbindungController: widget._bankverbindungController,
        isValidationError: _isPersonendatenValidationError),
    TextFormField(     <---Works
      controller: TextEditingController(
        text: DateFormat('dd.MM.yyyy').format(widget.gueltigAb),
      ),
      onTap: () async {
        ...
      },
    ).paddedOnly(top: 20),

The BankverbindungFormField is only another Stateful Widget which builds some Input fields i will use on multiple occasions.