Update:
TL;DR: I went ahead and updated from 1.14.1.5488 directly to 1.18.8.2527 and everything is running fine. Note that I’m running FreeNAS 11.2-U7
I use PMS_Updater.sh in my Plex jail. I quickly noticed that PMS_Updater.sh has been, uh um, updated. So I grabbed the latest version from GitHub. But then fetching the latest Plex version failed. I had to manually download the latest Plex tar file and use “-l” option to update manually.
I had to reboot all my clients and re-login as admin before any of the other Plex users could work. Not surprising, but just an FYI for anyone else trying this. You have to re-login as admin on your clients.
Everything is up and running fine now and PMS_Updater.sh seems to be working too.