Error: user autom4b not found

[Matth3wW]

I have docker running as root installed on a debian 12 LXC on proxmox 8.2.4. In config/auto-m4b-tool.log, I see the following message:

setuser: user autom4b not found

This is what docker logs auto-m4b shows

*** Running /etc/my_init.d/00_regen_ssh_host_keys.sh...
*** Running /etc/my_init.d/10_syslog-ng.init...
Jul 14 18:48:02 d0a80bbaa68c syslog-ng[14]: syslog-ng starting up; version='3.35.1'
*** Booting runit daemon...
*** Runit started as PID 22
Jul 14 18:48:03 d0a80bbaa68c cron[27]: (CRON) INFO (pidfile fd = 3)
Jul 14 18:48:03 d0a80bbaa68c cron[27]: (CRON) INFO (Running @reboot jobs)

This is the docker-compose.yml I am using.

version: '3.7'
services:
  auto-m4b:
    image: seanap/auto-m4b
    container_name: auto-m4b
    volumes:
      - /mnt/Audiobooks/autom4b/config:/config
      - /mnt/Audiobooks/autom4b/temp:/temp
    environment:
      - PUID=0
      - PGID=0
      - CPU_CORES=2
      - SLEEPTIME=1m
      - MAKE_BACKUP=N

/mnt/Audiobooks is an SMB cifs share from a windows machine.

Any help would be much appreciated! I am very new to docker, so I won't be surprised if this is just a basic user error.