Lose connection while modem renews internal DHCP?

I have static public IPs. Periodically my modem loses connection & requests a new internal IP. Though the new IP is always the same one. Clearly my public IPs are mapped to that internal IP. 

Why is the modem disconnecting? I have a global workforce & host servers on my network which cannot lose connection. 

Recent Event Log messages on the modem:

[Dhcpc][1532]: erouter0 got new IP x.x.x.x This frequently after the latter 

[Dhcpc][1543]: erouter0 T1 Expired, Enter Renew State This occurs frequently

[Docsis][549]: No Ranging Response received - T3 time-out This every few weeks