Maybe this would fix the problem I've had which is an h.264 render that looped over the first frame for the length of the in/out clip I had selected. Like it knew how many total frames it was supposed to deliver.. or it was stepping to the out frame, but it kept rendering the first frame over and over. This was after an initial render was successful. I went back to tweak settings and the subsequent renders had this 1st frame looping problem.
I'll test again later this afternoon after a reboot to see if I can replicate it.
That sounds very strange. Try removing the RSX and resetting everything.