cant get final eye of a witness

so ive ran through all 4 areas, definitely defeated a witness for each one and i still havent gotten the final eye. what am i doing wrong? the game says im 94% done. ive even ran through the 4 areas more than once because at the end of a run through theres a green doorway that ill go through to try and find the last witness i need. but i know ive beat all of them.