I'm configuring a pretty detailed set of ACLs in a Joomla 3.9.21 installation.
....and I almost lost my mind. Either I am a total dork, or Joomla has a major bug (or the database chaching is bitching around).
A user has access to 3 groups. These 3 groups allow to edit and publish articles in 3 categories.
Abilities (edit, publish) are managed via category permission.
Testwise I made some changes to the permissions. I changed permissions not in
"categories -> [category name] -> permission" but in
"articles -> options > permissions".
I revoked the changes I made, because suddeny the user got edit and publish abilities for articles in other categories.
So far so good.... I thought so... But the abilities persisted. The user was still able to edit articles in other categories. I fiddled for more than 2 hours... no change...
Then I created a new user and added him to exactly the same groups. And bam! It works. The new user has permissions as expected: Edit + publish for articles in three categories only. Check!

Why "bug" comes to my mind? The previous user (with exactly the same groups) still has permissons to edit + publish articles in other categories.

• I cleared all J!-caches
• I cleared my browser caches
• I quit and start my browser
• I tried with another browser
Am I a dork or has J! a bug?