I found a bug (i found it more than a year ago, but i've lost my Jira account, and i've got the access back today) that consists to make an iron golem INVINCIBLE. When the bug occurs, the iron golem is in like a "dead-alive" state (it looks like his health points went negative)

Here's a video showcasing it (and it still works as of today!) : https://youtu.be/BUWx-dT-z-0?si=Ckfh5XwUJgBWwalD