this happened to one of my bottles recently, and i put water in a pan on medium, untill i saw little bubbles, and then lowered it just to the point where the bubbles went away, put a pin as a vent, put set the bottle in the center, and swirled it every once in a while. i watched it to see the crystals resuspend, and then i added the same volume as was left in the bottle, from a bottle that didnt crash, heated a bit longer, and then it was fine.
be careful though, if the water is bubbly itl knock over the vial and it can spill out of the vent u made with the pin