Simulate motion vectors can fail on camera cuts

r.MotionVectorSimulation 1 should simulate motion vectors when cutting cameras, but this appears to be broken on some loops.

1. Create a sequence with a camera cut track and two cameras
2. Create two camera cut sections, one for each camera and transition between cameras in the middle of the sequence.
3. Animate a fast moving cube across both camera's views in the sequence
4. Add the sequence to a level and set it to auto play and to loop indefinitely 
5. PIE
6. Notice the motion blur on the cube
7. Enable motion vector simulation with r.MotionVectorSimulation 1
8. Screen record several loops of the sequence
9. Open the screen recording in an application that allows for frame by frame playback (e.g. VLC (E Key shortcut))
10. Step through frame by frame at each camera cut to see if the cube has motion blur on the first frame of the cut, this may take several loops.

RESULT

Some loops will clearly have no motion blur on the first frame after the camera cut.