We were re-uploading our old 10.3.3 format images to the new 11.2 format, with the Tuxera NTFS driver, and all was going well had a couple of them work with nice speed increases (40 minutes down to 12)! Doing another image, it uploaded fine, but failed to download correctly.

Every time we restored the image, at a certain point in the image, it would fail with "Unknown error code: 312". Re-uploading the image didn't help, the same thing happened multiple times. Long story short, the issue was some autocad language files in the image had Korean folder names. The full path was:
c:\programdata\autodesk\RAC 2012\Libraries\Korean_INTL

I opened the image with Image Explorer, deleted the entire folder, and now the image works correctly. If you need to use that folder, i have no idea, I don't really care, just posting this here to hopefully help someone who sees the same issue.