Photos distorted upon import. This keeps happening on and off. Sometimes LR imports perfectly, then I get distortions. I have removed the folder and reimported but no difference. The top photo is from Lightroom the bottom is from my computer file.
It looks like a hardware issue. It is a pretty frequent occurrence. The intact preview you are seeing (below) is the small embedded preview. The larger file (used by Lightroom) looks corrupted due to a data transfer issue. As has already been said, Memory Cards, Readers and Cables are the most likely culprit. Ports, Memory and Hard Drive are also considerations if testing the likely devices fails to bear fruit.