I see, there are something tricky in the ffmpeg conversion. It should be four dialogs in the clip, but turns out to have 8 chunks. The four dialogs are:00:00:03,934 --> 00:00:05,400, 00:00:05,400 --> 00:00:07,700, 00:00:08,300 --> 00:00:11,660, and 00:00:11,660 --> 00:00:14,960.
Please read the subtitle packets info of the uncut video here
https://www21.zippyshare.com/v/18bGYCpZ/file.html.
Despite that additional 0.033334 packets, the mov_text in ffmpeg simply adds many dummy packets so that each packet's end time = next packet's start time and each packet's start time + duration time = end time.
The start time is valid. The duration of each packet is ignored by LAV spliiter. I agree that the end time should be more robust against the case that next sample start time is larger than or not equal to current sample end time. If MPC-BE have worked well, maybe the duration handler of MP4/MOV Source was altered in the current version.
People using other player are complaining, too. I definitely need more information whether it is ffmpeg fault or not.