Подлагивает форма после вызова из menuItem WPF C#

Пишу приложение на WPF и столкнулся со следующей проблемой: запускаю окно при нажатии на кнопку, и все работает корректно. Но если запускать окно при нажатии на menuItem (или даже если при нажатии на menuItem вызывается метод обрабатывающий нажатие кнопки вызова окна), то форма подлагивает при поиске в таблице.

Код обработчиков событий:

private void Button_Click(object sender, RoutedEventArgs e)
    {
        Nomenclature_Click(sender, e);

    }

    private void Nomenclature_Click(object sender, RoutedEventArgs e)
    {
        if (this.nomenclature == null)
        {
            nomenclature = new Nomenclature(database);
            nomenclature.Show();
        }
        else
            nomenclature.Focus();
        this.nomenclature.Closing += (Nomenclature, args) => this.nomenclature = null;
      
    }

Код внутри окна:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;

namespace inventory_accounting
{
    /// <summary>
    /// Логика взаимодействия для Nomenclature.xaml
    /// </summary>
    public partial class Nomenclature : Window
    {
        public Database database;
        public Nomenclature(Database database)
        {
            InitializeComponent();
            this.database = database;
            tableSettings();
            addingEvents();        

        }
        private void tableSettings()
        {
            table.IsReadOnly = true;
            table.CanUserAddRows = false;
            table.CanUserDeleteRows = false;
            table.AutoGenerateColumns = false;
            table.ItemsSource = database.Products;
        }
        private void addingEvents()
        {
            find_code.GotFocus += Find_GotFocus;
            find_name.GotFocus += Find_GotFocus;
            find_quantity.GotFocus += Find_GotFocus;
            find_salePrice.GotFocus += Find_GotFocus;
            find_purchasePrice.GotFocus += Find_GotFocus;

            find_code.LostFocus += Find_LostFocus;
            find_name.LostFocus += Find_LostFocus;
            find_quantity.LostFocus += Find_LostFocus;
            find_salePrice.LostFocus += Find_LostFocus;
            find_purchasePrice.LostFocus += Find_LostFocus;            
        }



        private void Find_GotFocus(object sender, RoutedEventArgs e)
        {
            if ((sender as TextBox).Name == "find_code")
                find_code.Text = "";
            if ((sender as TextBox).Name == "find_name")
                find_name.Text = "";
            if ((sender as TextBox).Name == "find_quantity")
                find_quantity.Text = "";
            if ((sender as TextBox).Name == "find_salePrice")
                find_salePrice.Text = "";
            if ((sender as TextBox).Name == "find_purchasePrice")
                find_purchasePrice.Text = "";

        }

        private void Find_LostFocus(object sender, RoutedEventArgs e)
        {
            if ((sender as TextBox).Name == "find_code")
                find_code.Text = "Код";
            if ((sender as TextBox).Name == "find_name")
                find_name.Text = "Наименование";
            if ((sender as TextBox).Name == "find_quantity")
                find_quantity.Text = "Количество";
            if ((sender as TextBox).Name == "find_salePrice")
                find_salePrice.Text = "Розница";
            if ((sender as TextBox).Name == "find_purchasePrice")
                find_purchasePrice.Text = "Закупка";
        }

        private void Find_name_TextChanged(object sender, TextChangedEventArgs e)
        {
            if (find_name == null || database == null)
                return;
            var tmp = database.Products.Where(x => x.Name.StartsWith(find_name.Text, StringComparison.OrdinalIgnoreCase)).ToList();
            if (tmp.Count == 0)
            {
                return;
            }
            table.ScrollIntoView(tmp[0]);
            table.SelectedIndex = table.Items.IndexOf(tmp[0]);
        }
        
    }
}

Разметка таблицы:

            <DataGrid ScrollViewer.CanContentScroll="True" x:Name="table" AutoGenerateColumns="True" Width="auto" Margin="0,0,0,0" ColumnWidth="auto" FontSize="18" SelectionMode="Single"  >

                <DataGrid.Columns>
                    <DataGridTextColumn Header="Код" Binding="{Binding Code}" Width="auto" />
                    <DataGridTextColumn Header="Наименование" Binding="{Binding Name}" Width="auto" />
                    <DataGridTextColumn Header="Остатки" Binding="{Binding Quantity}" Width="*" />
                    <DataGridTextColumn Header="Закупка" Binding="{Binding PurchasePrice}" Width="*" />
                    <DataGridTextColumn Header="Розница" Binding="{Binding SalePrice}" Width="*" />

                </DataGrid.Columns>
                <DataGrid.Resources>
                    <Style TargetType="{x:Type DataGridCell}">
                        <Style.Triggers>
                            <Trigger Property="DataGridCell.IsSelected" Value="True">
                                <Setter Property="Background" Value="#CCDAFF" />
                                <Setter Property="Foreground" Value="Black" />
                            </Trigger>
                        </Style.Triggers>
                    </Style>
                </DataGrid.Resources>
            </DataGrid>