Looks like something else on your machine is using the port/address (giving Plex a address in use error). If there’s no other apps… have you already tried rebooting your QNAP to see if this sorts things?
I am having the same problem with the server, I’m using an Nvida Shield as my server, since the update its all messed up, I don’t understand why update something that isn’t broken and then break it with an update, I even have issues with remote accessing from outside the network, big issue know is I can’t even access Live TV & DVR via remote access please fix this issue