It's possible that when you are at war, circumstances will change and you'll e.g. end up with less money than predicted & your building won't be built.
Maybe there is something else. Do you have a reliable way to reproduce it?
For now it can't happen again. But I think it came from one big problem.
Now I can't declare war to a nation, when warring actions commited, The next turn, nothing happened... (the declared nation is still neutral).
I think that there is an action error, where actions is not executed properly.