I am farming UNM for 12 months now, perhaps longer, I do really not know any more. It seems that the chances getting lego books as cb loot have been worse during the last months. If it is rng, I do not know. Fact is, it feels like you are playing against the game not with it, if you do not cash at least three-digit a month. I've got approx. 20 Legos. All are missing of books. I'll never ever get that done, even if I would win every competition and would finish every event which is only affordable for whales.