This year we've learned that If a SOTA LLM decides that the sandbox is standing between it and its current objective: well, it has the ability, the time, and literally nothing better to do all day. Odds are, if you've configured the sandbox for anything useful, you've also provided a crack it can use to get out.
Again, doesn't make a sandbox entirely useless. Does mean you can't just put it in a really tight box and call the job done. If anything, the strict sandbox might even hurt, because it's more likely to get in the way.
(By analogy: consider the safety issues posed by a dam without a spillway.)