rendering Problem with DatePickerI18n in Datepicker

Flow
1

hi!
spring boot version:2.1.5.RELEASE
vaadin version: 14.4.2

when setting DatePickerI18n direct to Datepicker
z.b

Datepicker datepicker = new DatePicker(label);
DatePickerI18n i18n = new DatePicker.DatePickerI18n()
			.setToday("HEUTE")
			.setCancel("Abbrechen")
			.setFirstDayOfWeek(1)
			.setMonthNames(monthNames)
			.setWeekdays(weekDays);

datepicker.setI18n(i18n);

the datepicker will not be rendered sehe image_0

in case of setting I18n when openedEvent occurs
the datepicker will be partially rendered

this.datepicker.addOpenedChangeListener(event -> {
		event.getSource().setI18n(i18n);
});

see image_1

moreover when setting the DayNames to the I18n

List<String> weekDays = new ArrayList<>();
		weekDays.add("Montag");
		weekDays.add("Dienstag");
		weekDays.add("Mittwoch");
		weekDays.add("Donnerstag");
		weekDays.add("Freitag");
		weekDays.add("Samstag");
		weekDays.add("Sonntag");
	
	i18n.setWeekdays(weekDays)

this has no effect see image_1

using setLocale on Datepicker has no effect aswell
datepicker.setLocale(Locale.GERMANY)

many Thanks for the support

18565900.png
18565903.png