By unresponsive I mean it essentially acts like it does in a multiplayer game when there's a lot of lag - I order my fleets to do something, it shows that the order is queued, but they don't carry it out. Likewise, I click on a star system improvement and it does the animation of adding the improvement to the queue but it doesn't actually show up in the queue.

Anyway, I did some digging and I think the AI may be getting hung up on a decision. At one point with modding tools I was able to bypass it and continue on in the game, but in my attempts to figure out what went wrong in the first place I have been unable to reproduce that effect.

I went back and looked through the diagnostics files and found that one exception was happening in a loop hundreds of times. One of the diagnostics files even exceeded 200mb in size because of it. Here's a screenshot for quick reference, I'll attach one of the full files below.

Any ideas? 

EDIT: it won't let me upload the file so here's a link instead.