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.

Try removing the water bottle from the cooler? That’ll help you decide whether the emissions are from the bottle/water or from the compressor.

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.

Same here. I have 500Mbps service and speedtest more or less agrees. Fast consistently says it’s running at 700Mbps.

Looks much better.

Does your modem’s admin webpage report the signal levels that it sees?

It would be useful to compare the signal levels at the original location with the signal levels at the (slow) new location. It’s possible that there are multiple splitters (or possibly even a damaged cable) between the original location and the new location which would substantially lower your signal levels.