UPDATE: Synology support said there’s nothing I can do on the NAS side to solve the problem. Bummer.
Actually, I just had a look at a screenshot I took when I was documenting how to set up port forwarding, and my WAN IP never matched the public IP address shown in Plex. But the remote access and library sharing worked fine for a couple of weeks. @nokdim this suggests to me that there’s something else going on?
