It looks like it might be a case of when a file on the CFast card is read for a second, third or fourth time. Whether that be reading one of those subsequent times in the camera (connected to the computer through USB or Ethernet or even trying to process the raw inside the camera) or with the CFast card in the reader connected to a computer. Some of those who have mentioned not having experienced this corruption have mentioned that their workflow involves copying off the CFast card once to the processing or storage computer then not needing to read those same files off the CFast from that point onwards.
There has also been some speculation that a Mac OS reading the file the first or second time may be causing the corruption which has been supported to a small extent by the absence of people complaining of the problems using Windows machines. I'm not convinced on this score just yet as it just may be conincidence.