A 169 IP is assigned with the IPv4 protocal using DHCP can't reach a DHCP server through any external network device. Think of it as dialing a number and getting a fast busy. You have connectivity, but your computer or device can't go online. This is also seen as "Limited or no Internet connectivity" or "Discovering Network". Both of which stem from the network discovery service and a inability to know or reach the gateway.
Sounds like your router cant reach the modem's DHCP server(first 169) so the PC cant reach the DHCP server of the router (second 169), so the packets that were being transmitted at the time were dropped. That can be caused by alot of things. If your not actually seeing a connection problem, I wouldnt worry about it.