The sample is a part of randomly picked trailer just for testing.
Another
sample (should be fine now). When you go forward and backward through the video picking random frames, you will see at some moment that frames by 2.23.1 and r1327 are off. Then if you go backward to find the last I frame (let's call X the frame number) showed by 2.23.1, you will see that X frame by r1327 is B. If you refresh the video by r1327, the frame is still B type. Then if you go backward again to a place where frames by 2.23.1 and r1327 are the same and go forward frame by frame, X frame by r1327 will be now I frame and there will no further mismatch until you start picking randomly frames again. I encoded (x264) this sample with both 2.23.1 and r1327, and compared the encoded files - no matter how long I'm randomly picking forward/backward frames, the frames by 2.23.1 and r1327 are always matching.