@OneToOne - Error accessing field

@Data
@Entity
@NoArgsConstructor
public class Group {
 
    @EmbeddedId
    private GroupId id;
 
    @OneToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    @JoinColumns({
            @JoinColumn(name = "chat_id", referencedColumnName = "chat_id", insertable = false, updatable = false),
            @JoinColumn(name = "group_id", referencedColumnName = "group_id", insertable = false, updatable = false)
    })
    private Event event;
 
 
    @Data
    @Embeddable
    @NoArgsConstructor
    @AllArgsConstructor
    public static class GroupId implements Serializable {
 
        @Column(name = "chat_id")
        private Long chatId;
 
        @Column(name = "group_id")
        private Long groupId;
    }
}

@Data
@Entity
@NoArgsConstructor
public class Event {
 
    @EmbeddedId
    private EventId id;
 
    @OneToOne(mappedBy = "event", fetch = FetchType.LAZY)
    private Group group;
 
    @Data
    @Embeddable
    @AllArgsConstructor
    @NoArgsConstructor
    public static class EventId implements Serializable {
 
        @Column(name = "chat_id")
        private Long chatId;
 
        @Column(name = "group_id")
        private Long groupId;
    }
}