ARRIS S33 cable modem event log shows 31/12/1969 date when internet connection is dropped

The UNIX equipment that is defaulting the date to 1969 is the modem itself. When it is not online it can't get the Time of Day(ToD) signal from Cox to set it's virtual clock. Since the modem has no internal clock, it defaults to the UNIX birthday. The problem isn't the lost of date but the loss of connection that causes the loss of date. If you want to troubleshoot that, look at what the event logs are saying before the connection loss. T3/T4 errors?