ok so basically this is what happened: (wrong options assigned to some users after I changed few entries)

"Entries: (quoted from the custom profile field option)
Please note that you are able to change your options text and also able to add new options to the end. It is not advised to add new options between existing options - this could result in wrong options assigned to your users. This can also happen if you remove options in-between. Removing options from the end result in users having assigned this item now reverting back to the default one. "

how do I clean the users that have not selected anything? why does this happen anyway? isnt it a bug? why does it happen to the users only randomly?

Original support topic: https://www.phpbb.com/community/viewtopic.php?f=46&t=2167798