1996 Chevrolet Lumina I am not sure

I am trying to solve a problem with my friends car. Her father just fixed ball joint and the Axel on the front drivers side. Since he fixed that problem the car has been halting in reverse. Somewhat like if you have the e brake on. This doesn't happen every time we go to back up, but I have a infant and we feel unsafe in the car and are trying to figure out what is wrong with it so that way we can get it fixed right away. If you might have any idea to what might be wrong with the car please email me back asap. Thank you have a nice day.

Sincerely,
MeLinda S. Wisnasky