Yes you will come across these kind of issues if you choose to make a game that makes use of complex pathfinding. I have a rollercoaster tycoon type game with a ton of data but it's fun to handle. I would be careful of something that appears to be happening in that logic, it looks like the cooldown timer will be 0 when nothing is being built so it looks like the third event is regenerating the obstacle map every tick which is not good, unless you reset it to 3 somewhere. If you set it to 3 only on the start of construction then it seems to be an issue. Another problem I can see is that you don't seem to force the persons to leave, rather you set the building to solid based on the person leaving, so there could be a bug where you are waiting forever for them to leave and the building never becomes an obstacle for other people. Maybe you have an event further down which is if still on construction site then move them which would be useful.
Edit: Ok I see while I was typing you added a trigger once. Do you have an event that forces the persons to move? At the moment it just checks if they are there.