It's most certainly reproducible. The symlink /mnt/sd is being created, but not the actual device folder. You can do some scripting to remove the sd symlink and run "udevadm trigger --subsystem-match=block" to rescan and initialize the folder again, but this is something that I would imagine would need to be properly patched since the device could be used for photo viewing and it would be unintuitive to require reinserting the sd card on every reset. I found some udev waits that were set up to check a temp file to determine if there were USB devices waiting.

As for the debugchumby script, you can follow the path through /etc/init.d/rcS.background for the bootup process. It would probably be preferable to just create a hook in the /psp folder that would then branch to your sd card rather than writing to the root filesystem.