Sorry, yeah your right. I still need to upload that series. My older brother has hundreds of lectures backed up on CD, i checked them, and it is the same, some are cut off.
What often happens, is one brother purchases/records the lectures, and rips them from CD, and then uploads them onto the internet, or sends them to someone else who uploads them. Then everyone jumps onto the lectures, and upload them on their site, or by torrents. So most copyright lectures you see on the internet, came from one original source/person.
Its probably the same case here, there is probably only one set available on the net, so these are the most you will get.