Lightroom 5.5 Canon 5DIII raw files misinterpreted

Question

When I import Canon 5DIII raw files into Lightroom 5.5 some of the file end up with rectangular areas of garbage, often diagonal lines.
The problem is generally remedied by importing the file again.
I use Downloader Pro to get cards from the CF card and then import into Lightroom.
I have tried different memory cards but doubt this is the problem because reimporting same file generally solves the problem.

Answer 1

My guess is that the files are corrupted—part of the raw data is missing.  The slight curvature of the border is due to a lens profile being applied.
If the situation can be fixed by redownloading the file, then something must be happening in the transfer.
If this cannot always fix the situation then perhaps the card is bad and sometimes it works and sometimes it doesn’t.  If downloading the file multiple times always results in exactly the same corruption then I’d guess the image is on the card that way.  You can try using another way to download like Explorer or Finder, and see if the same situation happens.
If you want to upload one of the files that LR says is corrupted, others can test it to see if it is also bad on their systems.  Sometimes a computer’s memory is bad on the image will only look bad in LR, but usually this manifests as things streaks and spots, not a block in the corner.