I’m no pro here, but I just had the same issue after I added some content on my Plex Server on my RPi. I was getting a 401 when it came back to a local API on loopback. I found an old thread that suggested adding your local IPs to bypass auth.
I added the private IPs of my plex server to the ‘List of IP addresses and networks that are allowed without auth’ under Settings - Server - Network - ‘Show Advanced’ and metadata updates started working.
I’m now searching for why that workaround is relevant. My system is Linux and this other thread was more relevant to you being on FreeBSD and dealing with jails. If the workaround works it might be that this jail doesn’t have a loopback to source from so the server looks to auth a local request. That isn’t my issue, but hopefully, it helps.
