Update_User_Profile_Pre Hook Problem

hi i am try change custom profile field with hook update_user_profile_pre

its update when i edit profile fields from my profile details. but checkour step doesnt update custom profile filed

 $user_data['fields']['57'] = '';

i check fn_store_profile_fields everythink looking perfect but why doesnt work on checkout step ?

If your custom field is set to be seen on checkout page, then that data will be updated upon change to user_data.

You shouldn't have to use a hook to alter a custom field unless you want to use the value of that field to do something else.

You should check also fn_checkout_update_steps function (app/functions/fn.cart.php) and check how the profile data is updated

Yes i solve problem with adding custom hook