TAdvOfficeRadioGroup.RadioButtons[NewOwner].Enabled := False;

This does not occur on first use. On others, yes.

I have retested this here with the latest version and I cannot see a problem.
Test code on a default AdvOfficeRadioGroup with 4 items

procedure TForm3.Button1Click(Sender: TObject);
  AdvOfficeRadioGroup1.RadioButtons[0].Enabled := false;

and this works as expected.

If a problem persists with the latest version of the components, please prepare a sample source project & detailed steps to reproduce the problem.

Hm, maybe that's because I'm calling it from FormCreate.

Please provide sufficient details/sample source project to allow us to reproduce this with the latest version of the components.

Just paste the code in FormCreate

But I can solve this by inserting the code into the FormShow section

We fixed this. The next update will address this.