Do not forget to set properly attribute relationship type (rigid or flexible).

Do not forget to properly set the attribute relationship type (rigid or flexible). If you can, use rigid. If the relationship is flexible and a change is detected during processing, all aggregates are dropped. You will need to add them back manually (using ProcessIndexes process type). You will not receive notice from the server that aggregations are dropped. After aggregations are dropped you might noticed slower performance of queries. - Vidas Matelis