My images are being destroyed behind the scenes

I have 4 drives in two enclosures, both set to RAID 1.  Apparently, the backing up has copied the corruption.  I need to learn how to export the original SOC images that I imported and keep them set aside.  

"Is it not interesting that the preview thumbnail for the file shows the complete image?"

To build on thedigitaldog's answer, Finder and other apps use the JPEG thumbnail and JPEG preview embedded in raw files by the camera (and LR will use it initially for Library previews, depending on your Import options).  Experience on these forums indicates that when a raw is corrupted, usually the thumbnail (which is much, much smaller ) is left unscathed.  

Do you, as you should, have backups of the original photos?

It depends on the thumbnail, how and when it was generated. 

The big problem I see now is, when I try opening your .nef, it shows only part of the image as you've shown us. 

I even tried converting that .nef to DNG and I still see the same issue. Something has hosed that raw. 

Thank you for taking the time to look into that.  

Is it not interesting that the preview thumbnail for the file shows the complete image? 

The .NEF (6690) shows up in ACR as it does for you so yes, there is something corrupted in that document. Ditto for the Edited TIFF or course. 

So this looks like something drive-wise is the issue and you need to examine them all with a utility. Start with Disk First Aid (in Apple's Disk Utility), but that's not the most robust product around, but free. 

Your help is very much appreciated!  AND the plot thickens a bit.  after following your suggestions as well as closing LRC and rebooting the system, when I EXPORTED the ORIGINAL images to my desktop to then put in DropBox, once again the thumbnails on the desktop are complete.  Clicking on them, however, reveals the problem.  I have a small bit of hope the data is still there, somewhere.
Below is what my desktop showed after EXPORTING the corrupted files.  Then follows the dropbox link.

Corrupted LRC original files 

Please zip and upload that document to something like Dropbox. 

The Finder thumbnail isn't important here, the full document is. 

The GPU is not in use.  At your suggestion, I disabled every aspect of it and the problem persists.

Below is an export of the file (edited and saved as TIFF, exported a JPEG) with the All Metadata box checked.

In Mac FINDER, the selected thumbnail shows the complete image, but the preview tot he right shows the corruption.  
This, after making the changes above, closing LRC and rebooting the system.

Grid previews and those in Develop are not the same. In fact, previews in Develop are unique to all other previews throughout the application. So it could be GPU and until you try disabling it, we will not know. And we need a document you upload to know if indeed, the raws or other images are corrupted.