It seems to go away by itself. After a few hours it works fine.
I've seen 2012R2 dedup lock VBM files that causes backup to fail, could be related...
Before I applied the patch, I ran into the problem --- and it did not work fine later. Even on subsequent backups I still had the corruption.
It might have gone away after the third time I ran into the problem (post-hotfix), but I didn't want to meddle anymore.
I still have the scandisk error, so I'm done taking risks for now.
Interestingly enough, on another volume that is deduped but not being used by VEEAM, I've had no issues. Scandisk doesn't report any errors.
REFS, here I come. It's had some bugs but so far it's been more stable.