Problem

Under normal conditions, the popup content of SelectionBox updates correctly when itemsProperty changes.

However, in a rare but valid edge case, the update may silently fail:

If the itemsProperty is bound and changes before the popup skin is initialized, the "updatePopupContent" flag is set too early and never consumed—because the listener hasn't been registered yet. This prevents future updates from triggering.

Solution

Move the popup.getProperties().remove(...) calls into the updatePopupContent() and updateSelectionInPopup() methods themselves. This ensures the trigger flags are always cleared after consumption, even during delayed skin initialization.