ERROR: readlink /var/lib/docker/overlay2: invalid argument

[TurtleWolfe]

I've been trying to follow this tutorial;
How to create a docker-based LAMP stack using docker-compose on Ubuntu 18.04 Bionic Beaver Linux
and I thought I understood it fairly well, but I'm getting an error I'm not sure what to do about.
I can see the overlay referenced when I run docker info. I've tried pruning, removing, restrarting docker, restarting windows.. tempted to delete all the containers next.

docker-compose.yml

version: '3'
services:
    php-apache:
        build:
            context: ./php-apache
        ports:
            -  80:80
        volumes:
            - ./DocumentRoot:/var/www/html
        links:
            - 'mariadb'

    mariadb:
        image: mariadb:10.1
        volumes:
          - mariadb:/var/lib/mysql
        environment:
          TZ: "Europe/Rome"
          MYSQL_ALLOW_EMPTY_PASSWORD: "no"
          MYSQL_ROOT_PASSWORD: "rootpwd"
          MYSQL_USER: 'testuser'
          MYSQL_PASSWORD: 'testpassword'
          MYSQL_DATABASE: 'testdb'

volumes:
    mariadb:

repo: https://github.com/TurtleWolf/dockerLAMP

$ docker-compose up

ERROR: readlink /var/lib/docker/overlay2: invalid argument

[TurtleWolfe]

I'm not in the timezone he was writing this from.. should I delete that line? or set it to SYSTEM?