Do you run the program at home using a competition switch or field control ? Sometimes students see differences because of the way they have setup their code without considering how field control may enable/disable their robot at a competition (ie. when is the competition control cable plugged in etc.)
I seem to have linked this old topic multiple times lately, however.
The other thing that can be different is the field surface. Well used, perhaps dirty, field tiles will present a different friction to the robot wheels as compared to new field tiles. That can sometimes cause issues.