Having done nearly 100 technical interviews (with multiple questions each), the bug squash question gave us the biggest signal on candidates.
Our question was far simpler: it was a simple class (java + python variants, no fancy syntax) and ask them to describe what it does, then find the bug, and finally ask them what they would change.
It reflects a true test of what the day to day is, and whether or not the candidate would succeed in the role.