TYPO3 Core

So the following happened: Upon an import someone :trademark: accidentally imported the data of the table sys_category_mm twice but did not notice as there was not key. The Form engine or whatever could not handle this and deleted all categories attached to a record on the next saving of said record. In the fronted you did not notice a problem except in those places where all categories should be listed, there they where listed twice. To me it sounds like a core bug that sys_category_mm has (at least in TYPO3 v11) no key?

The bug seems to happen somewhere in the category tree or form engine. The TCA used for the affected fields is for example:

'wco_sitepackage_xyz_categories_for_submenu' => [
            'label' => 'Kategorien im Menü anzeigen',
            'config'=> [
                'type' => 'category',
            ],
        ],