I never dug into the failure, but I once had a ZFS get to a state where it would crash the kernel on mount, I was able to mount it with checks turned off an recover what was important, but it was a spooky experience. I live on the bleeding edge of file systems for my desktop, I was on reiser4 back when that was fresh, I daily drive bcachefs (it's been great!) Mostly I've been lucky, I don't usually keep an openbsd system around, but I love FreeBSD and I'll give OpenBSD a try with GEFS for sure!