The sort of corruption you're seeing is one I have experienced before. It is data corruption in the files themselves and doesn't necessarily indicate a camera or card problem at all. It can be due to a variety of reasons:
- Bad USB cables
- Bad USB card reader
- Bad USB port
- Damaged memory card
- HDD controller or HDD problems
- Faulty RAM on your PC
- Faulty camera
...and so on. Typically the corruption happens during the transfer from the card to computer, rather than on the camera itself. You can test this by reviewing the photos in the camera - if they look OK, and you can develop them in camera (using the 5D3 RAW development functionality), then it's easy to confirm the camera and card isn't the problem but actually the transfer process over to your PC. Conversely, if you see corruption on the camera without having involved the PC, then your camera and/or card is the problem.
I'd suggest trying different means of transferring photos to your PC (eg via USB from the camera itself rather than using a card reader, swapping USB ports and USB cables, copying to a different physical HDD etc) to try and narrow down the problem. Note also that you should NEVER use high speed UDMA 7 CF cards in a USB 2.0 reader - that can corrupt data on transfers, and in some cases even damage the CF card itself.
If you want to read more about this sort of corruption, there are various threads such as this one that might help:
https://forums.adobe.com/thread/356898