In my experience the problem is in the string that you have.
Es. "U.-SACO" is like a unit. If I am searching for saco, it will not appear becouse the search don't recognize the word in the middle of a string but from the starting point of the string. For searching what you want try to type "U.-s" ... One solution can be to divide this string in " U.-(space)SACO".
Es.2 in my index i have number with initial zero like 0675 so to find you have to search starting with zero. Typing 06, will find all 06* strings, typing 675 is finding nothing.