Set property not reached after an assignment

Question

I have a property in a ViewModel of my WPF project

        private Patient _Patient;
        [BindableProperty]
        public virtual Patient Patient
        {
            get { return _Patient; }
            set
            {
                _Patient = value;
                if (FormParameter != null) FormParameter.Value.Patient = Patient;
                InitializePatientSummary();
            }
        }

and I have a simple command to show a confirmation popup. If YES, I reassign Patient property.

        private void DeleteMDM()
        {
            if (ConfirmDelete(Resources.PatientFile_ConfirmDelete_Title,
                    Resources.PatientFile_ConfirmDelete_Body_MDM,
                    FormParameter.Value.MDM))
            {
                var mdm = FormParameter.Value.MDM;
                //_mdmController.Remove(mdm);

                Patient = FormParameter.Value.Tumor.Patient;
                ShowTumorImpl(FormParameter.Value.Tumor);
                FormParameter.Value.RaisePropertyChanged(x => x.Tumor);
            }
        }

This line _mdmController.Remove(mdm); is commented because it's an async operation and I would see if it can be the source of the issue but it doesn't.
Before assignee, I checked in the Immediate window Patient == FormParameter.Value.Tumor.Patient and it returns false.
FYI, I'm using DevExpress framework and this ViewModel doesn't have the [POCOViewModel] attribute.

It's clearly a basic operation but I can't find why the patient is not updated