I'm surprised I never ran into that before now, good find! I misunderstood that part of the API documentation, the game doesn't allow more than 18 entity types to be signaled per combinator. I've released version 0.16.3 which fixes that error. It does mean that in this situation, the signaler won't output all of the needed signals right away -- but as some parts of the blueprint are built, the remaining entity types will be signaled, so eventually everything gets signaled and built. So worst case, your train takes some extra trips, etc.
I could possibly improve this in a couple ways, like maybe split the signal requests between multiple Construction Signalers if you have more in the same logistic network. I'll think about it more.
