And that's why the bug went "back in time" - because yes it's the old code, but we were using a newer compiler with new default settings. In the original build, the compiler defaulted to x87, but in the newer compilers the default is SSE. It's not that one is "better" - the fundamental bug is that the guard was too close to the door, and that had always been there. But in the original the problem "self corrected" and so was never spotted, whereas in the newer compile it became a showstopper.