Product > Category autocomplete not working correctly

Hi, i'm having problem with Product > Links > Category autocomplete function. I have created many categories and sub categories and the auto complete function is only showing a few sub-categories in option box. A lot of sub categories are missing from the list even if type the full name in search box. how can i fix it?

You can try to find the 'missing' categories by using the wildcard % in the search box.
eg '%car' would also find 'ford 4wd cars'
Without the wildcard you'd have to type 'ford 4wd cars' in order to find it.

thank for help it is still showing few sub-categories and some are still missing from the list example: i have created 2 subjects categories 1. Physics and 2nd Chemistry and both have 3 sub-categories with same names. when i type the name physics it's not showing any sub category while if i type chemistry it is displaying the 3 sub-categories correctly. this the problem i'm facing.