This is caused by a hardware malfunction.
The fact that some viewers show the photo as uncorrupted is because these viewers are showing the JPG preview embedded in the file, which is not corrupted, yet the full RAW image (not shown by that viewer) has become corrupted. This is a regular and repeating characteristic of this issue. The fact that only a few images show this corruption is also a regular characteristic of this issue.
You need to try to figure out which of the hardware components involved (camera card, transfer hardware, hard disk and memory) are causing this corruption.
You are the second person to experience this. Another posted something very similar yesterday or early this morning. My first thought is as stated in the above post that it is a hardware or memory card problem. I'm still leaning in that direction but they both happened with Canon cameras. The other post didn't list the camera model. Could be the camera you are using has some problems
But IIRC Lexar is the most counterfeited memory cards. So it could be the card you have is counterfeit or your camera has a problem writing to that brand or size of card. First thing to do is get a brand new card from another manufacturer, Sandisk, and take a bunch of shots if no more corruption then it is the card. If you still get some images corrupted then it is the camera and you should contact Canon.