Thoughts? Prayers?
You can have both of these from me!
But just like in real life these wont solve any issues ;)
Jokes aside, it not swapping back might have something to do with the game not knowing what you want to optimize (armies/sec, money/sec, mine boost, etc).
However, given that the ACB was already there before, it can (and imo: should) swap it back.
If I was in your position I would probably just submit a bug report (Help > Contact > Report Bug), as it's an expensive item that doesn't work as expected.