Less number of changed objects in the database than the number of objects in list after Commit with a list

I am doing a number of change objects (the same attribute on the same object type) without commit and put them in a list during the process, only adding them to the list if the object is not found in the list, this list I am using at the end of the process to do the actual commit. But to my surprise, after the process, the actual number of  changed objects in the database is less than the number of list items!! So, where to look?
1 answers

If the attribute did not really change, Mendix may optimize the database commit and skip the unchanged objects there.