It's broken alright... that piece rattling around was the weight used on pendulum that senses the inertia from braking on the tow vehicle...
Here's a picture of what the inside should look like, with a similarly broken pendulum sitting at the bottom. See where your piece should have been attached?...

I don't think its serviceable, but you can try to remount the weight with some superglue, assuming the pendulum can be safely removed from its pivot.
For the money, you are better off with a Prodigy. The Voyagers run ~80, the Prodigy ~110. Spend the $30 for a more durable unit.
I had a Voyager for one trip in 2004, and returned it for credit towards a Prodigy, and never looked back on that decision. When we sold our fifth wheel, I sold the hitch on Craigslist, but kept the Prodigy, just in case we ever go back to a trailer.
Did the same with my Reese DC-WD -- kept it just in case because it is such a good hitch, but that is now on Craigslist as well...