@ThyReaper that was the problem! The construction can't be started when a creep is at the position.
I observed twice, that I can't build a ConstructionSite. To check that I stopped my Code (deleted main.js). Then I have a creep close to the construction and executed:
But the Command didn't work. After some ticks it worked then.... Around Tick # 11726786 (W13S37).
The game became Pay-To-Win, because to more CPU time you have, the more you can optimize your movements. Especially in war situations. Nevertheless, I changed that comment. BTW, I'm not angered by the recent change. The game dynamics develops in a very good direction.
I'm not interested to sympathize with you. I just promised in the screeps chat, that I share my code after I stop playing.
I'm not 100% sure, but I think I also noticed this behaviour.