The bug
If you throw in an iron golem potion of invisibility and do damage to it, the iron_golem_crackiness_* textures can be seen.
Linked issues
is duplicated by
Attachments
Comments

@unknown, did you even look at the video?

Tip for the future: Use OBS. That doesn't have this watermark and is pretty much the best screen recording software for all purposes.
Does MC-165967 describe your issue?