Remove all your $DefaultTopCar lines except the line that has
$DefaultTopCar = "XRG+LX4+LX6+RB4+XRT+RAC+FZ5";
otherwise you're confusing the program telling it one type of car on one line, but then saying it's a different car on another line, and then another different car on another line.
A poor analogy;
telling a computer program that
a+4=7
and that
a=1
a=2
a=3
a=4
And don't have "XRG+ because that's unfinished (needs either another car type added along with quote mark and semi-colon (e.g. "XRG+XRT";) or removal of the plus sign, and addition of quote mark and semi-colon (e.g. "XRG";)