I figure my DVDs and CDs don’t take much room. I have a few Case-Logic binders that hold about 400 discs each. They’re about the size of a medium-sized 3-ring binder.

What version of ZFS are you running? Are you using native ZFS encryption?

Run two scrubs and see if the problem goes away. Has to be at least two.

The problem here is that those independent backups would also be corrupted. As I understand from the github discussion, the issue might be a bug that causes ZFS to not recognize when a page is dirty and needs to be flushed and is somehow triggered when copying files using a new-ish optimization that has been implemented in Linux and *BSD kernels? If you trigger the bug while copying a file, the original remains kosher but the new file has swaths of bad data. Any backup made after this point would contain both the (good) original and (corrupted) copied file.