Paying for AA on resources without necessary MPPs

[Jkap]

There is a bug that allows you to sometimes pay for AA on a resource when you don't have enough MPPs. When you click on the upgrade arrow in the interface bar at the bottom, and then hover over the desired resource, you are occasionally able to get, for example: Level 2 AA with only 15 MPPs left.

I believe when I have had 11-13, it hasn't worked at all. Sometimes it just doesn't work when I have more than that but less than 20. Then it doesn't let me upgrade at all to level 2 (How it should be). I think I was also able to replicate this once in WiE as well. Maybe some other players have come across this.