this is a sign something is wrong with cron job. as you manual task runs I would sugest focus on differences from interactive to cron environment - but this more a base OS task rather NC related application problem so you better ask in the specialized OS forum. my guess would be either it doesn’t find docker command or it doesn’t find nextcloud-app-1
the recommended way to run NC background tasks in Docker is a “sidecar” container - review Docker .examples or docker-compose-setup-with-notify-push-2024 for details