Hey Spesius sorry to get back to you so late. Not sure how this slipped my radar!
The only way Oberlo can delete your products is through permissions set in the Auto-Updates. If the product reaches 0 quantity or is removed from Aliexpress, Oberlo has an option to have it removed in Oberlo too. Not sure what yours are set to, but I would suggest checking that out first.
You can find it by hitting Settings in the bottom left corner of your Oberlo app and scrolling down. There you should be able to turn this setting off so the product is not removed!
Let me know if that helps!