These are porcelain tiles I am referring to cracks like in the picture below They seem to be caused by the fact that the vertical force used to snap/crack the tile is applied at the opposite end and it is probably uneven or diminished at the other end of the tile
Ceramic tiles approved for flooring and porcelain tiles are much harder than the ceramic wall tile variants, and they require deep and continuous scoring in order to provide a straight snap cut.
When the snap cut curves away from the scoring line (as in your picture) it means that the scoring was not deep enough especially at and around the tile edge where the scoring starts (because it is opposite from where the tile is pressed to snap).
When scoring, apply more pressure and roll slowly.
Make sure the cutting wheel scores both ends around the tile edge, that is, the glazed top but also some of the ceramic side. After scoring once by pushing the lever and wheel forward, roll the wheel back and ride the tile edge a few times to make sure it is clearly scored. Do this for both tile edges.
Then snap with a rapid and firm movement of the lever.
Should this still fail, use a a tile nipper (or a wet saw) to score both ends deeper.