Problem when docker-compose down

[icychocolate98]

Good afternoon,

I noticed a problem if I delete containers or simply do docker-compose down ...
When I run again docker-compose up -d it wake up containers correctly but then when I try to "install-magento" in web container, I have this error:

In Installer.php line 903:
Missing write permissions to the following paths:
/var/www/html/pub/media/tmp/catalog
/var/www/html/pub/media/tmp
/var/www/html/pub/media/attribute/swatch
/var/www/html/pub/media/attribute

** it changes from www-data to root the permissions , I don't know why**

I can only fix it doing a new folder and starting process again ... It's important for me because I want to stop container and start again several times, or make several installations in different machines for example.

Any idea?