"Are there any known exploits apart from drilling?"
from an electronic point of view, i see one.
you have a direct acess to the opto-transistor from the 9v connector.
you don't have access to the driver, but perhaps you could fire it to force the current to pass
the goal is to open it, not to respect the limit to keep safe the components .
you have drill the box anyway ^^
let's continue in this way :p
i don't know if it work , but if you can unlock it with 5$ spend in batteries of 9v ...