do_action_ref_array( 'user_profile_update_errors', WP_Error $errors, bool $update, stdClass $user )

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This hook runs AFTER edit_user_profile_update and personal_options_update. If you want to validate some custom fields before saving, a workaround is to check the $errors array in this same callback, after performing your validations, and save the data if it is empty.

On return, if the errors object contains errors then the save is not completed & the errors displayed to the user.