Hello,
I've spend a bunch of hours having a bug with a set_relation_n_n :-(
void set_relation_n_n( string $field_name, string $relation_table, string $selection_table, string $primary_key_alias_to_this_table, string $primary_key_alias_to_selection_table , string $title_field_selection_table [ , string $priority_field_relation ] )
When the first parameter string $field_name contain a space, update and insert are not working !