Can't save entity with immutable collection twice within Transaction using Spring Data JPA / Hibernate

I have the following service layer function in my Spring Boot + Spring Data JPA application:

@Service
public class MyService {

    @Autowired
    MyEntityRepository repository;

    @Transactional
    public void serviceMethod() {
        MyEntity newEntity = new MyEntity("code", "name", "description");
        newEntity = repository.save(newEntity); // --> all good here

        // ...

        newEntity.setName("updated name");
        newEntity = repository.save(newEntity); // --> all good here

        Set<ChildEntity> newChildrenEntities = Set.of(new ChildEntity("childName"));
        newEntity.setChildren(newChildrenEntities);
        newEntity = repository.save(newEntity); // --> Exception here!
        
        // ...
    }
}

And when the execution reaches the last save method, an Exception is raised:

java.lang.UnsupportedOperationException: null
    at java.base/java.util.ImmutableCollections.uoe(ImmutableCollections.java:73) ~[na:na]
    at java.base/java.util.ImmutableCollections$AbstractImmutableCollection.clear(ImmutableCollections.java:79) ~[na:na]
    at org.hibernate.type.CollectionType.replaceElements(CollectionType.java:581) ~[hibernate-core-5.4.23.Final.jar:5.4.23.Final]
    at org.hibernate.type.CollectionType.replace(CollectionType.java:757) ~[hibernate-core-5.4.23.Final.jar:5.4.23.Final]
    at org.hibernate.type.TypeHelper.replace(TypeHelper.java:167) ~[hibernate-core-5.4.23.Final.jar:5.4.23.Final]
    at org.hibernate.event.internal.DefaultMergeEventListener.copyValues(DefaultMergeEventListener.java:451) ~[hibernate-core-5.4.23.Final.jar:5.4.23.Final]
...

If I switch the order of the operations, then the exception raises on the second method as well:

@Transactional
public void serviceMethod() {
    MyEntity newEntity = new MyEntity("code", "name", "description");

    Set<ChildEntity> newChildrenEntities = Set.of(new ChildEntity("childName"));
    newEntity.setChildren(newChildrenEntities);
    newEntity = repository.save(newEntity); // --> all good here

    newEntity.setName("updated name");
    newEntity = repository.save(newEntity); // --> Exception here!
}

However, if I change my newChildrenEntities implementation to a modifiable collection:

@Transactional
public void serviceMethod() {
    MyEntity newEntity = new MyEntity("code", "name", "description");
    newEntity = repository.save(newEntity); // --> all good here

    // ...

    newEntity.setName("updated name");
    newEntity = repository.save(newEntity); // --> all good here

    Set<ChildEntity> newChildrenEntities = new HashSet<>();
    newChildrenEntities.add(new ChildEntity("childName"));
    newEntity.setChildren(newChildrenEntities);
    newEntity = repository.save(newEntity); // --> all good here!
        
    // ...
}

Or if I remove the @Transactional annotation from my method, then everything works ok.

I'd like to know why exactly this happens, it seems related to how Hibernate handles collections.