[TYPO3-mvc] Repository-Query with sys_category ignores category_mm[tablenames] field

[Daniel Hirth]

Hello,

we stumbled upon another category-related issue: 

There two models, catalogue and event, both make use of the sys_category integration. Events are automatically imported via scheduler task from an external source. Usually, this works fine. But we discovered that sometimes, after the event import scheduler task has finished, the categories of some catalogue-items were missing.

I'm 99% sure that the importer script is responsible for removing the categories of the cataloge items, because this problem only appears directly after the script executed (or even while it executed). In the import script, we assign a category to every event-item before persisting:

if (!empty($category)) {
     $event->addCategory($category);
}

Is this the same problem we ran into before, only this time for writing MM Relations, and not for reading? Or doesn't it have to do anything with this? 

Regards
Daniel