The problem could possibly be more than 25 feet away. If the kitchen sink drains into the same pipe, there may be an area that is partially full of grease. Usually running water and augering back and forth will take care of that (if there is some kind of head on the auger cable…a plain straight cable or tape can just go through the grease without moving it). And you could have a broken drain pipe, an indication might be dirt coming back on the auger cable.
