I've not seen this one covered elsewhere, and whilst I've already tried the Feedback Assistant to get it to Apple, I'm not sure if it's being picked up or looked at there...
The problem I've encountered is that whenever I use Disk Utility to create an APFS encrypted volume within a container, it works, but only until I reboot. When I reboot, after looking in I'm prompted for the password for the volume. I'm 100% certain of the passphase I used, but, after entering it the UI "shakes" to indicate the passphrase was wrong. If I try again, either with the same passphrase, or, trying something like my login password, the UI will go away, but, the volume does not mount.
In Disk Utility I get the error:
Could not mount “Data”. (com.apple.DiskManagement.disenter error 49218.)
And that's that. I've now lost some data permanently, which is a bit frustrating. I excluded that volume from TimeMachine backups to ensure that there weren't unencrypted copies of the data floating about anywhere (even though my TM volume is encrypted (HFS+, not APFS)).
Sadly, this is 100% repeatable, and I've had it happen a few times. Thankfully, not much data has been lost forever, but, it makes it tough to trust APFS Encryption.
Steps that I took to do this:
1) Had a new HD inserted in my MacPro (2019)
2) Drive was formatted with GUID partition map
3) Initial APFS container created (no encryption)
4) Once Container existed, as well as initial whole-disk-sized APFS volume, I clicked on the Container and "+" to create a new container.
5) Chose APFS Encryption as the FS, generated a passphrase with 1Password, and am certain it's accurate.
6) Volume mounted just fine, was able to read/write data to it no problem
And that's where it went off the rails.
Has anyone had better and more reliable experience with APFS Encrypted volumes?