We have just noticed a problem with physics synchronization when time_smooth is used (assuming that fps_lock is also used which is a good idea). Physics objects may appear to occasionally jump forward every N frames due to rounding errors combined with time interpolation caused by time_smooth

Solution: set time_smooth=0 at the very beginning of your main !

Sorry to bump this, but this is another thread that would be nice to have as a sticky and thus we stay "on top" (pun intended) of the current engine status.