Getting some really weird behavior from our Ubuntu server... it's behind a Verizon router firewall with port forwarding (port 8080 to port 80 on the server), and we've been having issues accessing it via this external IP. From within the network, it appears to respond normally (I can access it via web browser and SSH), but refuses connections through port forwarding (using our static external IP). The strangest thing is that it actually responds to external port-forwarded connections right after being restarted, but quickly lapses back into this pattern of refusing external connections.

I'm a bit of a server newbie (I'm actually a programmer in a small startup that just lost their server ops guy, urgh) so this is all trial by fire for me. Does anyone have any advice on what could be going wrong here? Any help would be appreciated, thanks.