Thymeleaf - Checked attribute of checkbox is not set in th:each OR how to properly restore a list of checkboxes some of which were previously checked

In my app I want to create a new Risk ( an instance of Risk object ) and when it is created I want to display 5 checkboxes and three radio buttons. Selected options are specific to each instance of Risk object.

Later I want to display a list of all added Risks with an Edit option button on each Risk. I want my app to restore the view specific to a selected Risk ( when an Edit button on a selected risk is clicked ) - with Risk name, all checkboxes and radio-buttons checked as selected previously. And I want to be able to edit these checkbox selections again so that all new changes were properly reflected in MySQL.

As a newbie in Thymeleaf I did the following:

<div th:each="top : ${topic}">
    <input type="checkbox" th:field="*{topic}" th:checked="${top.checked}" th:value="${top.name}"/><label th:text="${top.name}">Something is wrong !</label>
</div>

I am sure that Controller and Hibernate/MySQL part works properly ( I checked using Logs ).

This works just fine - but only if I have selected only one checkbox ( initially when I added a risk ).

If I select more than one checkbox (when adding a risk) and later select this risk for editing no checkboxes are checked.

What is wrong ?