ssh fails: image not found [preauth]
dtruss shows:

2892/0xdc8e:  stat64("/usr/lib/libsandbox.1.dylib\0", 0x7FFF500DA5F0, 0x7FFF500DB500)        = -1 Err#2


which is ENOENT (No such file or directory) and the reason is probably that chroot already happened.  If you are so foolish as to experiment by

sudo mkdir -p /var/empty/usr/lib
sudo cp /usr/lib/libsandbox.1.dylib /var/empty/usr/lib


You will move the crash to the next shlib not under /var/empty/

sshd[3256]: fatal: ssh_sandbox_child: sandbox_init: dlopen (/usr/lib/libsandbox.1.dylib, 261):
Library not loaded: /usr/lib/libsqlite3.dylib\\n  Referenced from: /usr/lib/libsandbox.1.dylib\\n  Reason: image not found [preauth]


If you persist with this madness

sudo cp /usr/lib/libsqlite3.dylib /usr/lib/libMatch.1.dylib /var/empty/usr/lib/


sshd will start to work again at least for SSH keys, passwords still don't work.

You can also edit /usr/local/etc/sshd_config changing

UsePrivilegeSeparation sandbox


into

UsePrivilegeSeparation yes


But outside of debugging purposes I don't suggest trying any of this.