If you are ever having trouble with multi select property controls (list box multi select or input multi select), go to the Edit menu > Document Properties > Property Controls and take a look at the values. Not all "multi select" properties work the same way.  Take note of the screen shot below, specifically the last two.  In this example, I created a ListBox (multi select) control and an input (multiple lines) control, and you can see that the input control is concatenating the values.  The list box is not.  Instead they are separated by a comma.  This is why these two controls are not always interchangeable.