Docker user can't access shared data folder

I'm new to forums, so sorry if this is the wrong place for support. I'm also somewhat new to Linux. I'm trying to run Navidrome using the docker-compose plugin, with this config:

services:
  navidrome:
    image: deluan/navidrome:latest
    user: 1002:100 # should be owner of volumes
    ports:
      - "4533:4533"
    restart: unless-stopped
    environment:
      # Optional: put your config options customization here. Examples:
      ND_SCANSCHEDULE: 1h
      ND_LOGLEVEL: info  
      ND_SESSIONTIMEOUT: 24h
      ND_BASEURL: ""
    volumes:
      - "/data"
      - "/srv/dev-disk-by-uuid-a9fe2d21-4082-492e-9478-2b02c5b46ab0/Music"

I created a user with minimal permissions (it's in the groups docker, omv-admin, omv-config, sambashare and users) to run the container and set it as the owner of the data share using the ACL panel. I also explicitly gave it read/write perms using that menu. When I bring up the container, I get this error in the log:

navidrome-1  | FATAL: Error creating cache path: path /data/cache mkdir /data/cache: permission denied

I'm wondering why it can't access a folder that it owns and that I explicitly allowed read/write access to. I'm sure that I used the correct user and group IDs. If I comment out the user field it starts up successfully but for some reason can't rind the music in the music folder (logs say it's empty but it's not), but I guess that's a different can of worms. I don't want to run it as root.

If this is relevant, I'm running OMV on an x86 CPU and the data share is on an M.2 drive, while the music share is on an HDD.

Quote from chente

You have made many mistakes. I suggest you take a look at this and start again. https://wiki.omv-extras.org/doku.php?id=omv7:docker_in_omv

Thanks for pointing me in the right direction, previously I was going off of dubious Youtube tutorials. I should've read the manual!