Upgrade to 13, zfs issues

Hi,

I'm planning to upgrade my kitchen server to stable/13
Machine :
IBM SE7525GP2 (quite old, I know) Dual Xeon, 8 GB Ram, PCI Marvel AHCI
SATA controller 88SE9215
Disk layout :
rootfs on ufs (SSD) attached on onboard atapci controller
zfs pool storage not involved in boot (4 HDDs on ahci controller)

To check potential issues before starting, I've tried to boot the server
into mfsBSD via PXE using : 
https://mfsbsd.vx.sk/files/iso/13/amd64/mfsbsd-13.1-RELEASE-amd64.iso

When booting mfsBSD, the boot loader fails, last messages on console are
ZFS: Inconsistent nvlist contents
ZFS: Inconsistent nvlist contents

<register dumps>
BTX halted

Is this expected, please ?

zpool status and zdb don't report any outstanding issue on the pool.

Regards

Éric Masson

-- 
 > On peut aussi trouver une façon de modifier l'adresse pour déclancher
 > les soupçons des impôts, histoire d'être aussi chiants que lui ?
 -+- ALG in : GNU - Neuneu a recommandé son percepteur -+-