Saving true DNGs from RAW files

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Shot about 70 RAW files on 5D Mark III today. The first 5 were fine. The next 20 were not. The final 40 were fine.
The ones that were not are producing alternating frames from RAW file #5 and another random file throughout all 20 unpacked DNG folders.
The RAW files are correct in size. Can someone tell me these are salvageable on a Mac? Any help is much appreciated   thanks, Dan