This is because the problem is with the main file, not the chapter file. We replaced the entire parent video file on July 4th, but some of you are still accessing the old file, which is either cached on your device or is cached on one of our cloud content servers.
We just purged the cache on our cloud servers (this may take up to 24 hours to take effect). I would suggest trying again and see if it is working correctly for you now. It's working fine here, but it may take longer for the cache purge to reach the cloud server you access. Also, you may need to clear the cache on your machine, too, but try it again now and let us know if it is working correctly.