How is it unstable? Not trying to be mean, just curious.
It's like playing hot potato. The "hex" is unstable and will explode after an unknown amount of time so you need to pass it. The more it gets passed around the more unstable it gets. Also holding for a few seconds will also increase the instability. The meter at the bottom of the UI is supposed to give you, the player, an indication of how unstable or close to exploding the hex is.