I believe 3.1 was refering to the surround channels and center plus sub in a 5.1 system. not 3.1 as in front 3 plus sub. I should think if it cuts out running 2 surrounds and the center then it must be getting very hot.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70