A DESCRIPTION OF THE PROBLEM :
`getItems() `not use `itemsProperty()` to obtain the corresponding items property, but instead directly called the `items` variable

https://github.com/openjdk/jfx/blob/600cee70a2f6f907a53f7183315e6d7f79b291d6/modules/javafx.controls/src/main/java/javafx/scene/control/ComboBox.java#L313