Express Delivery

I see it quite a lot when I try levels out for testing to check levels players have complained about. Invariably yes, the next board will be slightly easier, but never easy enough to pass without boosters. So it's a method to encourage players to part with their boosters to get this special "treat". Also, yes, it invariably means you will be stuck for a long time yet on the level if you don't take the bait. But I do find that usually a little further down the line a better board will come along. Most of these horrible levels eventually let you pass with starting boosters, but I am yet to find a method to spot when this will happen, as playing starting boosters for every try is not an option for anyone who isn't cheating to get them.

Does anyone know how often this train shows up? Like after how many attempts at a level or is it just random?