Same happened with me, while I was streaming live on Instagram on my Prime 4 V2.1.1.
I was in the middle of the set, then I loaded a track in deck 2 & baammmm!!! The gear hung and restarted. It was very embarrassing. Upon restart, I selected the same track again, so it restarted again.
One reboot takes about 30 seconds. 
It was for that particular track only.