Form dropdown (MultipleSelector) does'nt show values

create a new Process model with one variable of type list. add a script task to create a list of String values and add them to the process variable. add a human task and assign the process variable as input data. create a ui form for the human task. Add the list variable as type 'MultipleInput' (unselection the readonly option). run the process and open the task form. Good - values are shown (see screenshot). modify the ui form. Remove the form element and add it again but as type 'MultipleSelector' (unselection the readonly option). run the process and open the task form. Failure - values are shown (see screenshot). I expect that the values from the list variable are shown in the dropdown.