as per my post above
when you use removeAll you also remove the __dataProvider array

example -

PHP Code:
_level0.combo.__dataProvider = [object #127, class 'Array'] [ 
    
0:[object #128, class 'Object'] { 
      
data:undefined
      
label:"animal" 
    
}, 
etc... 
then use - combo.removeAll();
PHP Code:
_level0.combo.__dataProvider = [object #125, class 'Array'] []
// empties the dataProvider array