login plugin kept loosing my password when using docker-grav project

STEPS

Here is the whole story

i have a docker desktop on my windows 10 computer working with linux containers
For what it worths :
Docker Desktop : Version 4.2.0 (70708)
Engine: 20.10.10
Compose: 1.29.2
Credential Helper: 0.6.4
Kubernetes: v1.21.5
Snyk: v1.563.0

DAY 1
i have cloned the https://github.com/getgrav/docker-grav project
use the docker-compose.yml provided with the docker-grav README.md page "Running Grav Image with docker-compose and a volume mapped to a local directory"
I changed the port (using localhost:9000) because my 8080 port is already used.

i have fired docker compose up - so far so good, i can see grav on localhost:9000

i went to localhost:9000/admin

i have been prompted with the user registration form. i created my administrator account with my usual password (familiar, it's the one i use on my local project)

i have been playing with Grav the whole day with no problem

End of DAY 1:
turned the container off quite violently with Ctrl+C twice (it stopped the container and force killing it)

DAY 2
fired docker compose up again

went to localhost:9000/admin

tried to log in with my yesterday administrator account : the login page said the _login failed_

i thought i was careless and set a wrong password... googled a little for it and somebody said all i had to do is to delete the user/accounts/administrator.yaml file and go back to the admin page, the user registration form should be prompted again.

that's what i did
- deleted the yaml file
- went back to the admin page -> no user registration form
- restart the container
- went back to the admin page -> after a LONG while, been prompted the user registration form
- registered a new administrator user _AGAIN_
- wrote the password down on a paper, just in case

Played with Grav the whole Day 2 with no prob

Turned the container off with Ctrl+C twice

DAY 3
fired docker compose up again

went to localhost:9000/admin

tried to log in with the administrator account : the login failed _AGAIN_

ISSUE
I can't log in Grav Admin with a registered user

EXPECTED
when a user is registered, i should be able to log in Grav Admin with the same user and the same password the following days

Start with the docker-compose.yml and the “Running Grav Image with docker-compose and a volume mapped to a local directory” section of the docker-grav README. Reproduce the administrator login failure across container restarts, checking the user/accounts/administrator.yaml path and the localhost:9000/admin entry point. Done means a registered administrator can log in after subsequent restarts using the same password.

Written by the indexing model from the issue text.