As is visible in the screeshot (two Ranger Camps on the top left), some of the buildings wouldn't unselect after being placed. Placing buildings in general was pretty floaty and sometimes took a few tries.
You couldn't move already placed buildings anymore (as in, they were impossible to even pick up) and the card selection starts to be hard to click with a lot of cards. I think that's it.
Honestly though, I was pretty amazed that the game still ran at all, I was putting quite a bit of a strain on it