Pass Uniface-application object between units

Hi, I have a working (windows application) uniface-test, and now trying to divide this up into re-usable parts (units). So 1 of the first things I need to do is open the application and pass it on from one unit to another. When I run tis I get the following message: "Unable to find the object MDIClient. See Details for additional information"

Anyone an idea what is going wrong here?

Here are my 3 units:

Unit 1 = start unit:

var unitTZISAPP = require("TZISAPP");

var unitTZISAPP_LOGON = require("TZISAPP_LOGON");　

function CallTestObjects(){

let TZisApp = unitTZISAPP.letZisApp();

let returnvalue = unitTZISAPP_LOGON.TZisAppLogOn(TZisApp);

Log.Message(returnvalue);}

Unit 2 called TZISAPP:

module.exports.letZisApp = letTZISAPP;　

function letTZISAPP(){

//Start application

return TestedApps.Tzis.Run();}

Unit 3 called TZISAPP_LOGON:

module.exports.TZisAppLogOn = TZISAPPLogOn;　

function TZISAPPLogOn(TZisApp){

let wndUniMDIFormLogOn = TZisApp.MDIClient.wndUniMDIForm;   => ERROR ON THIS LINE

let uViewPortLogOn = wndUniMDIFormLogOn.uviewport;

let uniCanvasLogOn = uViewPortLogOn.UniCanvas;

let editLogOnUserName = uniCanvasLogOn.Edit;

editLogOnUserName.Drag(46, 8, -86, -1);

editLogOnUserName.SetText("x047593");

let editLogOnPassword = uniCanvasLogOn.Edit2;

editLogOnPassword.Click(30, 11);

editLogOnPassword.SetText(Project.Variables.Password1);

let btnOKLogOn = uniCanvasLogOn.OwiCmdButton.btnOk;

btnOKLogOn.ClickButton();

return 1;}