With some 14.0-CURRENT based experimental ISOs, we get a kernel panic:

mdconfig -a -t vnode-o readonly -f /boot/rootfs.uzip
(...)
panic: guz_zstd_decompress: Expected 262144 bytes, got 163840
(...)
KDB: stack backtrace:
(...)

This is the FreeBSD source code in question:
https://github.com/freebsd/freebsd-src/blob/627f1555f571b5328637dbfbe441ed89c84db20c/sys/geom/uzip/g_uzip_zstd.c#L81

• Build 0H55 does not panic
• Build 0H56 panics (only change was to include a self-built pkg of drm-510-kmod which is not even loaded yet at the stage where the crash happens)
• Build 0H59 (a mere re-run of 0H56 without any code changes) also panics in the exact same way
• Build 0H59 (reverted to the same contents as 0H55) does not panic again

Conclusion: It seems like with some contents or with some size of the contents, the mdconfig -a -t vnode-o readonly -f /boot/rootfs.uzip step fails at guz_zstd_decompress.