Yeah, we know about the ZFS encryption with send/receive bug, it's frustrating our attempts to get really nice HA support on our logging system... but so far it appears that just deleting the offsending snapshot and creating a new one works, and we're funding some research into the issue as well.
in case you want to ballpark-estimate your move off of the cloud
Bonus points: I'm a Fastmail customer, so it tangentially tracks
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Quick note about the article: ZFS encryption can be flaky, be sure you know what you're doing before deploying for your infrastructure.
Relevant Reddit discussion: https://www.reddit.com/r/zfs/comments/1f59zp6/is_zfs_encrypt...
A spreadsheet of related issues that I can't remember who made:
https://docs.google.com/spreadsheets/d/1OfRSXibZ2nIE9DGK6sww...