Mapping error : More than one row with the given identifier was found

I'm working on a spring boot application and i'm using JPA and hibernate.
I'm facing a problem with the mapping relation between two entities User and Evaluation.
the main idea is to evaluate a user via another one (evaluaters)

User.java

public class User implements Serializable {

    private static final long serialVersionUID = 1209816669845063949L;
    @Id
    @GeneratedValue
    private int idUser;
    private String login;
    private String password;
    @ManyToMany(mappedBy = "listUsers")
    private List<ProjectGroup> listProjectGroup;

    @OneToOne(mappedBy = "EvaluatedUser")
    private Evaluation evaluation1;
    @OneToOne(mappedBy = "Evaluater")
    private Evaluation evaluation;
}

Evaluation.java

public class Evaluation {

    @Id
    @GeneratedValue
    private int idEvaluation;
    @OneToOne(cascade = { CascadeType.PERSIST, CascadeType.MERGE })
    @JoinColumn(name = "evaluateduser_fk")
    private User EvaluatedUser;
    @OneToOne(cascade = { CascadeType.PERSIST, CascadeType.MERGE })
    @JoinColumn(name = "evaluater_fk")
    private User Evaluater;
    @OneToOne(cascade = { CascadeType.PERSIST, CascadeType.MERGE })
    @JoinColumn(name = "project_fk")
    private Project project;

    @OneToOne(cascade = { CascadeType.PERSIST, CascadeType.MERGE })
    @JoinColumn(name = "notes_fk")
    private Notes notes;
    }

EvaluationController.java
I'm using this method to return all the evaluations

@GetMapping(path = "all-evaluation", produces = {"application/json" })
    public ResponseEntity<List<Evaluation>> getAllEvaluations() {
        List<Evaluation> list = evaluationService.findAll();
        return new ResponseEntity<List<Evaluation>>(list, HttpStatus.OK);
    }

The problem is, i can't evaluate the same user twice, i think the problem is with my relation OneToOne
This is the exception i'm getting while returning the json :

There was an unexpected error (type=Internal Server Error, status=500). More than one row with the given identifier was found: 1, for class: com.talan.entity.Evaluation; nested exception is org.hibernate.HibernateException: More than one row with the given identifier was found: 1, for class: com.talan.entity.Evaluation

Any help would be apreciated