This probably has to do on how you target the symbols.
Here is an example:
you have a symbol named car with a label named start.
Here is how you target its timeline:
var car= sym.getSymbol("car");
^ What resdesign said.
A more explicit (and verbose) way to express the above example (perhaps this makes it clearer?):
//get the symbol "car" and play it from its "start" label
And of course, ask questions.