Not respected categorization

Thanks for reporting the issue and the pointer to the possible cause. It was indeed due to the form putting blocks and categories at the same level with category ID and block ID as array key. I simply prefixed the categories array keys with 'category_' . $category->id() to make it uniq. These keys are not used in the submit so it does not have any impact.

Automatically closed - issue fixed for 2 weeks with no activity.