ZFS: inconsistent nvlist contents

Hello freebsd-questions@

I've begun seeing "ZFS: inconsistent nvlist contents" on the screen on reboot on
a 13-stable desktop system recently. makeworld happens monthly on average.

The system is not root-on-zfs. There's more than one zpool.

The message happens after the bios has probed for disks but before the (legacy) 
beastie displays. It's not captured in dmesg - one needs to be looking at the screen
while it's booting to see it.

1. what's implied by the error message?

2. do i need to take any action, or worry about it?

3. is there a fix?

The system has no nvme/m2 hardware. It's strictly ssd and ada* (sata)

thanks in advance for any advice,