I don't consider this post a spoiler, since there is only general information about how to avoid being unable to complete the game. If anyone reading this post doesn't want ANY information about Puzzle 12, don't read this.

The only MAJOR roadblock that many people encounter is that you need a master builder to complete puzzle 12, and you won't have one when you need one if you don't plan carefully. That isn't the only requirement, and I'll refrain from giving more detail, except to say that it can be completed much earlier than its position on the puzzle screen would suggest (as soon as you have the necessary levels of Village Tech and the required villager).

There are no other pitfalls that I'm aware of that will "toast" your village or your chance to complete the game.