How to properly update input type="radio" value in Angular 2 ReactiveForms?

Question

Angular

Good afternoon everyone, a situation arose with Angular 2 in which I can’t finish it. The code, with a problem, was isolated from the project, without any extra. Link to Plunker
You can reproduce the problem like this:
1) Select a button that has flag: true. For example Item #1. The form data is substituted correctly, the radio becomes True
2) Next, select the button with flag: false (either from the preset Item #3, Item #6) or the one for which there is no entry in the data list. The form data is again substituted, as expected, and the radio switches to False as intended.
3) Select the button again, with the False flag. And here comes an incomprehensible situation, the title is substituted correctly, but the radio in False is not checked, it turns out that not a single radio is selected, if you select the button with flag: true again, everything will fall into place, but if you select False again, and then False again, the problem will repeat, has anyone encountered this garbage? How to fix?