Hmm, really need support to wade in on this because as mentioned the whole unit is shutting down.
I know it has protection on the power amp but yeah the sound just temp stops, not the unit shutting down. Also if you just pull the speaker lead out with sound, it doesn;t reboot.
Dodgy lead could be a possibility as mentioned but certainly not normal behaviour - difficult to tell from the vid but I think I've played as loud as that no issues.
Hope you get it sorted dude!