We have the same trouble in my country, where dancers slip onto the wrong beat. The problem seems to be , this is of course if you can hear the beats correctly, that a person arrives with all their weight on 4 and has nothing to do on 1, which should be a hip movement only. This is where it gets tricky. You should arrive on 4, heel down on the beat of four, but don't move your hip over untill the count of one. To add a little more. I wonder if you know the importance of getting your heal down right on the beat. In the case of a New York the toe must arrive before the beat to enable me to get my heel down on the beat. That is why the steps are being counted in half beats. On every half beat there is an action. My teacher, a former top international professional, tells us that a step is just a step. It is in between the steps where we dance. Good Luck.