299 MHz is docsis 3 freq there must be something wrong with the levels for the modem to do this . The super hubs will drop the 6 or 8 downstream channels and go from 2 or 3 upstream channels to 1 it's a self preservation mode it will still let you get on the net but not the speeds you expect . It will go back if the problem goes ie noise on the node or Ingres on the node . W
If the modem does connect to more than 1 ds and 1 us check the levels
