Spring JPA entity doesn't update when i use getReferenceId() in transactional function

Question

The contents of the database do not change despite the normal communication and modification of the contents to be modified through the DTO.

entity code like this

@Getter
@ToString(callSuper = true)
@Table(indexes = {
        @Index(columnList = "title"),
        @Index(columnList = "createdAt"),
        @Index(columnList = "createdBy")
})
@Entity
public class Article extends AuditingFields{
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Setter @Column(nullable = false) private String title; 
    @Setter @Column(nullable = false, length = 10000) private String content;

    @ToString.Exclude
    @JoinTable(
            name = "article_hashtag",
            joinColumns = @JoinColumn(name = "articleId"),
            inverseJoinColumns = @JoinColumn(name = "hashtagId")
    )
    @ManyToMany(cascade = {CascadeType.PERSIST, CascadeType.MERGE})
    private Set<Hashtag> hashtags = new LinkedHashSet<>();

    @OrderBy("createdAt DESC") 
    @OneToMany(mappedBy = "article", cascade = CascadeType.ALL)
    @ToString.Exclude 
    private final Set<ArticleComment> articleComments = new LinkedHashSet<>();

    @Setter @ManyToOne(optional = false) @JoinColumn(name = "userId")
    private UserAccount userAccount; //유저 계정 id

    protected Article() {} 
    public Article(UserAccount userAccount,String title, String content) {
        this.userAccount = userAccount;
        this.title = title;
        this.content = content;
    }

    public static Article of(UserAccount userAccount, String title, String content) {
        return new Article(userAccount, title, content);
    }

    public void addHashtag(Hashtag hashtag){
        this.getHashtags().add(hashtag);
    }

    public void addHashtags(Collection<Hashtag> hashtags){
        this.getHashtags().addAll(hashtags);
    }

    public void clearHashtags(){
        this.getHashtags().clear();
    }

    @Override
    public boolean equals(Object o) { 
        if (this == o) return true;
        if (!(o instanceof Article article)) return false;
        return this.getId() != null &&  this.getId().equals(article.id);
        
    }

    @Override
    public int hashCode() {
        return Objects.hash(this.getId());
    }
}

problem method like this

public void updateArticle(Long articleId, ArticleDto dto) {
        try {
            Article article = articleRepository.getReferenceById(articleId);
            UserAccount userAccount = userAccountRepository.getReferenceById(dto.userAccountDto().userId());
            if (article.getUserAccount().equals(userAccount)) {
                if (dto.title() != null) {
                    article.setTitle(dto.title());
                }
                if (dto.content() != null) {
                    article.setContent(dto.content());
                }

                Set<Long> hashtagIds = article.getHashtags().stream()
                        .map(Hashtag::getId)
                        .collect(Collectors.toUnmodifiableSet());
                article.clearHashtags();
                articleRepository.save(article);
                articleRepository.flush();

                hashtagIds.forEach(hashtagService::deleteHashtagWithoutArticles);

                Set<Hashtag> hashtags = renewHashtagsFromContent(dto.content());
                article.addHashtags(hashtags);
            }
           
        } catch (EntityNotFoundException e) {
            log.warn("error", e.getLocalizedMessage());
        }
    }

Strangely, when you call the "Article" class through the "findById" function, it updates normally

when i call updateMethod, entity modified right away

I guess the cause was related to "lazy loading". Or maybe "Entity Manager" can't do "dirty check"?

I would appreciate it if you could let me know the cause of the above mentioned problem and how to solve it.

Please understand that I may not be able to express my English properly because I am not good at it.