Ah yes, have to favorite that job...
My favorite source of admin cap evaporating is the time some idiot proposed denouncing one of the fallen empires in the War in Heaven, which caused 95% of the galaxy, including me, to be in violation of galactic law and imposed something ridiculous like -40% admin capacity due to other resolutions. On top of naval cap and research penalties, of course.
The worst part is that as far as I can tell you can't reverse it. Ever. According to the galactic community screen it's a galactic focus, so after 10 years I proposed shifting the galactic focus to the Prethoryn Scourge, which barely passed because the AI being eaten by them didn't convince it they were a serious threat. Despite that passing, the galactic focus remained on that fallen empire, which I guess is hard coded by the War in Heaven.
Later, after destroying said fallen empire out of frustration, the War in Heaven ended, but the focus remained and I was still in violation of galactic law because I did not join the Unknown Empire in their war against the Unknown Empire. At least by this point all of the negative resolutions had been repealed by the galactic community because everyone realized being crippled like that was bad. I considered leaving the galactic community but wanted to see how far the bug would go, and if anything would ever happen from the sternly worded letters that presumably literally everyone in the galaxy was receiving from everyone else.