In the file you give, you can see that cubes have a negative scale factor. So, instead of being repulsive, the force is attractive. Funny and good to know. It might even be useful in some cases. But, in order to put things back to normal, just put positive scales. And it is also a good idea to apply scales before running the simulation (ctrl-A and apply scale).
Best regards.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…