Random rebooting

Main box is rebooting at random and whenever we attempt to go to the XF-menu, to anything saved, or into streaming APPS.  The bedroom box works fine.  The Main TV works fine using SAMSUNG TV instead of XFINITY.  It only reboots when it is on HDMI through the main box.  I have added a UPS battery unit as the power source - didn't help.  The same COAX runs throughout the house and works okay in bedroom.  Should I just get a new/replacement X1 box?  Or, if it is a COAX cable issue, does Xfinity help with COAX problems, or is that something I need to have someone else work test/fix?