Did you guys edit the ini files? I think that might be the problem. The game stuttered a lot so I changed some settings in the ini files, and it helped the stuttering. I started having problems with the game sometimes not progressing properly, though. I never had this problem prior to editing the ini files. So, I threw away the entire config folder that contained the ini files so the game could recreate them to their default settings. The game worked properly from then on. The game also seemed to have less stuttering, although it could just be my imagination.
If you didn't mess with the ini files then I'm not sure what to.