Steps to reproduce the issue

It seems there is a bug on J4/J5 for mod_articles_categories ("This module displays a list of categories from one parent category.").

In the Module, select a Parent Category

• which has Sub-Categories
• having in turn Sub-Sub-Categories

Expected result

We should have a nice hierarchy

• with Sub-Categories
  • and their respective Sub-Sub-Categories

Actual result

Each Sub-Sub-Category appears twice

• ✅ correctly as child of their parent
• ❌ but also a second time at the same level as their parent

System information (as much as possible)

Was working fine under J3.
Issue tested both on J4 and J5.

Additional comments

Cassiopeia is not having any override for this module (only for mod_menu and mod_custom) so the issue would be

• at the Joomla level
• and not at the Cassiopeia level