What are you using the judge that the corruption isn't in the original CR2 files?
What is likely happening, and a screenshot would help understand more, is that the raw data is corrupted in the CR2 files but the camera-embedded JPG near the beginning of each CR2 file is ok, and whatever software you're using to view the CR2 files outside of LR is only looking at the embedded JPG not decoding the actual raw data. More detailed information would help determine if this is the situation.
Another possibility is that the lines of corruption are not in the raw data but only in the display of the files on the computer, and there is some failing hardware or software component on the computer causing the issue.
If the raw data is corrupted, usually a rectangular area starting at a certain position of the image has odd colors from there to the end, whereas if there is a hardware or driver failure, then only pixel-thin lines of various colors are sprinkled here and there on the image.