Shutdown causes a pool lock

TrueNAS General
1

I recently added an Optane SLOG and since when I have shutdown, using

shutdown -p now

and in each case on reboot the pool is locked:

LOCKED    lock This geli-encrypted pool failed to decrypt.

After recovering by removing the SLOG and adding it back all is well.

Does anyone have an explanation, please?

2

It could be an edge case related to GELI encryption, have you considered migrating to a ZFS-encrypted pool?

Storage Encryption | TrueNAS Documentation Hub.

3

Yes, it did occur to me, but I was procrastinating, hoping the issue lay elsewhere.
Thanks for the nudge,