Hi Colin.
I managed to record this a few days ago and already shared the video with Jack. Were you playing in 2D or 3D? If it was 2D, did the cars line up on the grid with the pole sitter already around the first corner like this...
This screen shot was taken at about the same time using the 3D viewer...
I think the reason the race looks wrong in 2D is because of the offset, the cars appear to slow down part way along the DRS straight in 2D because they're actually just rounding turn 11 coming on to the straight. This may also be why DRS "appears" to activate part way down the straight.