>>265120191
This happens if they go out of sync with the connection points. A tracker is a type of controller, and they 'mount' to specific endpoints. The headset has two, and can support two controllers. So that's why you have three dongles, one for each tracker. 
So what you probably did is exhaust your endpoints accidentally by having one endpoint marked as used when it wasn't. 
I recommend repairing everything, and then with 'manage trackers' stick your trackers to have positions instead of being generic controllers.