WPF drpdwn SelectionChngdEventArgs not firing after making pckge for plug

Rhino Developer
1

Hi all,
After building a package my designed WPF form doesnt react as expected. Dropdowns are filling with items, but they dont fire the Selectionchanged events.
Boilerplate works as expected.
Below a piece of the code.

public void BrandsoleSelectedLeft(object sender, SelectionChangedEventArgs e)
        {
            
            SizeSelectionBoxLeft.Items.Clear();
            RhinoApp.WriteLine("brandole selected");
            Insole brandsole = new Insole();
            brandsole.SelectedBrandsoleFilePath = textFormat.BrandsoleTextFormat(brandsoleTemplatePath, brandsoleFileInfos, BrandsoleSelectionBoxLeft.SelectedIndex);
            RhinoApp.WriteLine(brandsole.SelectedBrandsoleFilePath.ToString());
            importObject.ImportBrandsole(brandsole, out brandsole);
            setSizesTable.SetSizeTable(brandsole, out brandsole);

            foreach (double size in brandsole.SizesTable)
            {
                SizeSelectionBoxLeft.Items.Add(size);
            }
        }

Can you help me out?
Thanks in advance
Regards Reinder