During one particularly annoying episode where it effectively became a DOS I had my router log all dropped packets and then rebooted it. Immediately after reconnecting it drops a few incoming martians and invalid packets as if they were still expecting an active connection where there shouldn't have been any. The IPs were mostly upstream endpoints or gateways but at least once it was from a residential IP instead.

Between the weird arbitrary nature of the SSL/TLS handshake issues and the possible spoofing from upstream gateways I get the impression this is much more than just a bug.