it's kind of strange to me that ad-hoc debugging is considered such a valuable skill. I thought it's mostly a juniors' perspective. I typically set up extended loggers and logger methods, write everything to the some formatted file, and have a diffable, persistent, provable, multithread-friendly and versioned bug demonstration, which scales well to bugs of any complexity.

(I once found some 10 bugs in a pretty old and tested bond calculation engine while migrating it to the cloud, which nobody could initially believe.)