As I stated above. rolling back and pinning the kernel to 6.5.13-5 stops this from happening on my Microserver G8.
I should also point out that I'm using the built in sata controller in AHCI mode so I'm unsure if this will still happen with another HBA installed.
Further to this: The buggy firmware in the HP Gen8 Microserver (bios J06 04-04-2019 is the latest) will cause kernel 6.8 to corrupt ZFS pools with unrecoverable errors on my PBS server. Rolling back to 6.5.13-5 prevents this.
Glad I have two PBS servers with sync enabled.