All of this was done primarily in an attempt to fix the issue, including reinstalling the game, but to no avail. The game can still be launched using project8.exe from the directory, but when launched through Steam, it shows the same error. It seems to me that the problem lies in Steam's file...
I have the same problem, but this is definitely not a non-standard path, since my laptop only has one system drive and the installation path is standard for Steam. I’ve been playing since June, and the problem suddenly appeared around September 4th, along with it came stuttering, but most likely...