You have quite a lot of restricted area (with permission set to 0)
The problem comes from the fact that media don't have individual access rights. They get the rights that are granted to the namespace they are in.
With your current ACL
* @user 0 members of group user have no right at all for anything (including any namespace)
* @smr 1 members of group smr have read access for anything (including any namespace)
* @ALL 0 members of other group and anonymous users have no right at all for anything (including any namespace)
No other ACL for any other namespace. So theses rules will apply to any namespace.
The rest of the ACL gives various rights (read write) to some pages only. But their rights on media are governed by the acl set on the namespace.
This is thus normal that non admin (ACL don't apply to admins) users not member of smr can't see the images.
Also, note that there is no "upload" user. With your current config, only admins may upload. upload rights are 8+
I suggest that you review
https://www.dokuwiki.org/acl and fix the ACL.
Maybe, what you need is like this, if monitor is a namespace and not page. (
but I can't know, it all depends on the structure of your wiki)
monitor:* @smr 0
monitor:* @customer 1
If you have a flat wiki (no namespace), giving rights on media but not on pages will be almost impossible. Because you must give at least read access on the whole wiki (* @smr 1) in order to give access to the media and explicitely remove rights for any page that the members of the group smr should not access. You would end up with hundreds of rules, and each new page would require new ACL. multiply by the number of groups, and you get an idea of the problem. You might have to reorganize your whole wiki, pages and media.
I see no reason why the upgrade tool would change the ACL.