Well the amount of objects in that level might be it. Or a very specific object, since that sandbox has more types of objects in it than any of the other levels do. What platform are you running? Does anything show up in the error console? I had a similar issue about that once before, and it was because of some error that was cropping up and slowing down performance on Windows/Linux, but not Mac OSX.There is probably a slight performance drop due to all the objects in that one sandbox level, as screen capturing slows it down quite a bit, but not the other levels, and it takes longer to load the resources in it (I'm going to have to implement some form of background loading for that eventually). However, if it is an actual error like the one I had last time, I would very much like to fix it.