Contour 2 mini boxes randomly shut down and ask to be rebooted.

Random shut downs of my mini boxes and they require restart.  I exchanged the boxes at the Cox store - they are still shutting down.  The helpdesk sent a reboot signal to both boxes, it happened again with one box.  All connections that I can reach are tight.  I even reset the internet gateway - still having problems.  Help, please!  I do not want to go around in circles with the helpdesk again.