Error issues on omv docker Mariadb and Nextcloud

I follow the below instruction to install nextcloud with docker and docker-compose.…g-OMV-and-docker-compose/

when I use a directory in the system disk as data volumes, everything is alright. The nextcloud run correctly.

When I repeat the whole install, only change the volumes of Nextcloud and Mariadb to the external disk, the first page of nextcloud comes to freeze after click “finish setup” and “504 Gateway Time-out” appears.

I tried serval time and can’t go through this step. no error in the docker app logs.

What 's this mean? something wrong with the database or nginx?