Select all doesn't work properly when using data provider at grid (Vaadin14)

I am using Vaadin 14 (14.1.17) and data provider with multi-select. When I hit select all button, the rows aren't selected at UI but they are selected at backend(grid.getSelectedItems() works). In addition, when I select one row and then hit select all button, grid.getSelectedItems holds the previous value, so it gives grids.size() + 1 instead of unselecting the previous value that was selected before.

My data provider and bean are like this:

@Entity
@EqualsAndHashCode
@Table(name = "forms", schema = "click", catalog = "")
public class FormEntity {

    private long id;
    private String userId;
    private String requestorType;
    private String confirmationPhone;
    private Timestamp submittedDate;
    private int status;
    private Timestamp approvedDate;
    private String comments;
    private String organization;
    private PatientEntity patientEntity;


    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id", nullable = false)
    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    @Basic
    @Column(name = "user_id", nullable = true, length = 70)
    public String getUserId() {
        return userId;
    }

    public void setUserId(String userId) {
        this.userId = userId;
    }

    @Basic
    @Column(name = "requestor_type", nullable = false, length = 50)
    public String getRequestorType() {
        return requestorType;
    }

    public void setRequestorType(String requestorType) {
        this.requestorType = requestorType;
    }

    @Basic
    @Column(name = "confirmation_phone", nullable = true, length = 50)
    public String getConfirmationPhone() {
        return confirmationPhone;
    }

    public void setConfirmationPhone(String confirmationPhone) {
        this.confirmationPhone = confirmationPhone;
    }


    @Basic
    @Column(name = "submitted_date", nullable = false)
    public Timestamp getSubmittedDate() {
        return submittedDate;
    }

    public void setSubmittedDate(Timestamp submittedDate) {
        this.submittedDate = submittedDate;
    }

    @Basic
    @Column(name = "status", nullable = false, length = 11)
    public int getStatus() {
        return status;
    }

    public void setStatus(int status) {
        this.status = status;
    }

    @Basic
    @Column(name = "approved_date", nullable = false)
    public Timestamp getApprovedDate() {
        return approvedDate;
    }

    public void setApprovedDate(Timestamp approvedDate) {
        this.approvedDate = approvedDate;
    }

    @Basic
    @Column(name = "comments", nullable = true)
    public String getComments() {
        return comments;
    }

    public void setComments(String comments) {
        this.comments = comments;
    }

    @Basic
    @Column(name = "organization", nullable = true)
    public String getOrganization() {
        return organization;
    }

    public void setOrganization(String organization) {
        this.organization = organization;
    }

    @ManyToOne
    @JoinColumn(name = "patient_id", referencedColumnName = "id", nullable = false)
    public PatientEntity getPatientEntity() {
        return patientEntity;
    }

    public void setPatientEntity(PatientEntity patientEntity) {
        this.patientEntity = patientEntity;
    }
}


 private ConfigurableFilterDataProvider<FormEntity, Void, Map<String, Object>> getFilteringDataProvider(OrganizationDto organizationDto) {


        DataProvider<FormEntity, Map<String, Object>> dataProvider =
                DataProvider.fromFilteringCallbacks(
                        query -> {
                            Map.Entry<String, String> sortOrder = null;
                            List<QuerySortOrder> sortOrderList = query.getSortOrders();

                            if (!sortOrderList.isEmpty()) {
                                QuerySortOrder querySortOrder = sortOrderList.get(0);
                                sortOrder = new AbstractMap.SimpleEntry<>(querySortOrder.getSorted(),
                                        querySortOrder.getDirection().name());
                            }

                            Map<String, Object> filter = query.getFilter().orElse(null);

                            List<FormEntity> rv = null;
                            rv = registrationService.fetchForms(organizationDto.getIdentifier(), filter, query.getOffset(), query.getLimit(), sortOrder).getContent();
                            System.out.println("List size:" + rv.size());
                            return rv.stream();
                        },
                        query -> {
                            Map<String, Object> filter = query.getFilter().orElse(null);

                            long count = 0;
                            //The second callback finds out how many items there are in total in the datasource matching with current filters.
                            count = registrationService.fetchForms(organizationDto.getIdentifier(), filter, 0, 1, null).getTotalElements();
                            System.out.println("Count:" + count);

                            return (int) count;
                        }
                );

        return dataProvider.withConfigurableFilter();
    }