Plex picks the wrong interface on a QNAP (essentially it's a lottery from amongst anything with a defined default gateway: could be the correct interface, the vswitch NAT for container station, the vswitch NAT for vstation, etc. etc. etc.), and there is currently no way to influence its fundamentally poor choices.
Forums have been asking this problem to get fixed for SIX YEARS -- since 2012.
really, even if it's not exposed as a GUI knob, how hard is it to add a parameter to tell Plex daemon which interface to listen on?
so, the question is: hey devs, when is this going to be fixed?
(and if it's not ever going to be fixed, will you admit that, so we can abandon QNAP as a platform for Plex)
All Your QNAP Users.