I think this might be something to do with the TrueNAS install/docker itself.
I get exactly the same problem, with exactly the same error, when trying to install WebDAV.
root@truenas[/var/log]# docker logs ix-webdav-permissions-1
exec /usr/local/bin/python3: input/output error
exec /usr/local/bin/python3: input/output error
Could something have become corrupted in the .ix-apps folder please? If so, how can I remediate without a complete reinstall of TrueNAS?