I am experiencing the same problem that was logged in 2016 and cannot see that a solution was posted or any updates. The gist:
I bought Canon 1DXII, it comes with Sandisk 128 CFast card + Reader:
The card reader heats up after a very short while - I have a PC and some of the RAW files on the cFast card are corrupted (at the lower right corner).
I updated the firmware to the latest available version and the problem persists. I also did a hard format on the cFast card and still, the problem persists. I have only used the card three times.
Some Raw file shows corrupt, but when I let the card cool down and insert again, it reads some of the “preview not available” photos.
Is there a fix for this problem?