Problems with rolling starts in freeplay using back of the pack mod

Lately, I have been having problems using the back of the pack mod in freeplay when using rolling starts. As the cars are rolling, a large number of the cars slow down to where the cars are hitting each other in the back. It also seems that one or several cars at the front get separated from everybody else in the process. I’m not sure what could be causing other than it might be a bug from an content update.