Yea there's a huge element of randomness to these kinds of interviews. I wasn't a big fan of them at Stripe. You can get some signal like:

- do they methodically approach the problem? - do they understand the bug? - do they know how to use debugging tools? - do they know advanced debugging tools? - do they work well in an unfamiliar codebase?

But in practice I'd say most candidates check those boxes, at which point it becomes an arbitrary evaluation unless you pass/fail them based on whether they solved the bug.