During synchronization a new object was found through a relationship that was not marked cascade PERSIST

Hi everyone,
i have 3 entities: USER, GROUP and PRIVILEGES made like this:

public class Users {

@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "IDUtente", nullable = false, precision = 18)
@Id
private BigDecimal id;

@Column(name = "GroupLevels")
private Long groupLevels;

@JoinColumn(name = "IDGruppo", nullable = false)
@ManyToOne(fetch = FetchType.LAZY, optional = false)
private Groups iDGruppo;

@Column(name = "IDItem")
private Long idItem;

@Column(name = "IDTAb")
private Long idTab;

@JmixGeneratedValue
@Column(name = "ISrowguid", nullable = false)
private UUID iSrowguid;

@Column(name = "Parameters", length = 50)
private String parameters;

@Size(message = "{msg://com.company.configuratoreutenti.entity/Users.password.validation.Size}", min = 8)
@NotNull
@SystemLevel
@Secret
@Column(name = "Password", nullable = false, length = 50)
protected String password;

@InstanceName
@NotNull
@Column(name = "Username", nullable = false, unique = true, length = 50)
protected String username;

@JoinColumn(name = "SysLevel", nullable = false)
@ManyToOne(fetch = FetchType.LAZY, optional = false)
private Privilegi privilegi;

#########################

public class Groups {

//@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "IDGruppo", nullable = false)
@Id
private Integer idGruppo;

@InstanceName
@Column(name = "DESCRIZIONE")
private String descrizione;

@JmixGeneratedValue
@Column(name = "ISrowguid", unique = true)
private UUID isRowguid;

@OneToMany(mappedBy = "iDGruppo")
private List<Users> users;

@OneToMany(mappedBy = "iDGruppo", cascade = CascadeType.ALL)
private List<GestRisorse> gestRisorses;

public List<GestRisorse> getGestRisorses() {
    return gestRisorses;
}

#############################

public class Privilegi {

//@GeneratedValue(strategy = GenerationType.SEQUENCE)
@Column(name = "SysLevel", nullable = false)
@Id
private Integer sysLevel;

@JmixGeneratedValue
@Column(name = "ISrowguid", unique = true, nullable = false)
private UUID iSrowguid;

@Column(name = "permessi", length = 20)
private String permessi;

@NotNull
@InstanceName
@Column(name = "Privilegio_Utente", length = 100)
private String privilegioUtente;

@OneToMany(mappedBy = "privilegi")
private List<Users> users;

When I create a new user and assign it the group with id 0 I get this exception:

Immagine 2023-06-14 171839

this exception only appears when i link user with group id 0, if i were to link any other group i can make user creation correctly

Thanks in advance

This error usually indicates that entity you save references another new entity that hasn’t been merged into the DataContext. The reason is somewhere in your screens code, I guess. Try reproducing your problem in a separate small demo project - maybe this will give a hint on what you’re doing wrong.