Answer by Mark Kaplun for what effective ways are there to debug cron

While @Wyck's and @vlood's answers are good for many scenarios, I ended up with another way to isolate where the problem might be by just directly surfing to example.com/wp-cron.php which in my case triggered properly all events which means that the problem is most likely with the wp cron lock mechanism which uses the doing_cron transient.