getDuration() gives wrong value. bug?

I have a simple Symbol with a timeline of 10 seconds.

If i place a any trigger  like sym.stop()  anywhere "on the timeline" sym.getDuration() gives me 10000 what ist correct.

If i place no triggered action on the timeline sym.getDuration() gives me 170454.41228624 which is quite not correct.

Its in the same EdgeAnimate - Compositon and clearly reproducible.