Did a pro shoot yesterday. First 400 shots uploaded fine. Last 40 have colored bars across them and are corrupted files. Tried uploading just those 40 again. No luck. Using Nikon d750. Files are RAW NEF. Using sands 32 extreme pro. Loading on iMac sierra. Thx
This is a hardware malfunction somewhere. It could be camera cad, card reader or USB cable/USB port, hard disk or computer memory. You need to try to import the photos again using different hardware to isolate the problem.