App for printing Dymo labels disables scalling when print

Question

I've made a little app for printing Dymo labels and it works as intended, but when I run it on my Surface tablet it disables scalling af I've pushed the print button. If reopened the scalling is correct till print button is pushed again. Can anybody tell me why?

The print button only runs my LabelPrinter class which has the following code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Dymo;
using System.Windows.Forms;

namespace LabelPrinter
{
    class LabelPrinter
    {
        private DymoAddInClass dymoAddIn;
        private DymoLabelsClass dymoLabels;
        private string labelPath, classRoom;
        private int labelCount;

        public LabelPrinter(string labelPath, string classRoom, int labelCount)
        {
            dymoAddIn = new DymoAddInClass();
            dymoLabels = new DymoLabelsClass();

            this.labelPath = labelPath;
            this.classRoom = classRoom;
            this.labelCount = labelCount;
        }

        public void printLabels()
        {
            dymoAddIn.SelectPrinter(dymoAddIn.GetDymoPrinters().Split('|')[0]);
            if (dymoAddIn.Open(labelPath))
            {
                int firstNo = StaticMethods.getNextCodeEntryWithString(classRoom), lastNo = firstNo + labelCount;

                dymoAddIn.StartPrintJob();
                for (int i = firstNo; i < lastNo; i++)
                {
                    foreach (string objName in dymoLabels.GetObjectNames(true).Split('|'))
                    {
                        dymoLabels.SetField(objName, classRoom + "_" + i);
                    }

                    dymoAddIn.Print(1, false);
                }
                dymoAddIn.EndPrintJob();
            }
        }
    }
}