The issue seems to come from

FReply UNoesisInstance::NativeOnKeyChar(const FGeometry& MyGeometry, const FCharacterEvent& CharacterEvent)
{
    SCOPE_CYCLE_COUNTER(STAT_NoesisInstance_OnKeyChar);
    if (XamlView)
    {
        TCHAR Character = CharacterEvent.GetCharacter();

        bool Handled = XamlView->Char(CharCast<char>(Character));

        if (Handled)
        {
            return FReply::Handled();
        }
    }
    return FReply::Unhandled();
}

CharCast<char> lose important character information.

It's been fixed. If you want to apply the change locally, change the cast to CharCast<WIDECHAR>(Character).

Thank you.