The Bug:
Iron Golem cracks are outlined by the glowing effect.
Steps to Reproduce:
Summon a damaged Iron Golem with the glowing effect.
/summon minecraft:iron_golem ~ ~ ~ {Health:74f,Glowing:1b,NoAI:1b}
→ ❌ Notice how the cracks are outlined by the glowing effect.
Information:
This issue clones MC-173834, which was fixed in 21w10a, however, it has reappeared again in 21w11a.
Linked issues
Attachments
Comments

Also, only iron golems with intermediate levels of health have their cracks outlined. When the golem's health becomes very low, the cracks stop being outlined. This behavior is the same for both MC-173834 and MC-220270, and this behavior was previously mentioned in this comment from MC-173834.
Example
/summon minecraft:iron_golem ~ ~ ~ {Health:90f,Glowing:1b,NoAI:1b}
The golem does not have cracks, so obviously the cracks aren't outlined.
/summon minecraft:iron_golem ~ ~ ~ {Health:74f,Glowing:1b,NoAI:1b}
The golem has cracks and they are outlined.
/summon minecraft:iron_golem ~ ~ ~ {Health:24f,Glowing:1b,NoAI:1b}
The golem has cracks, but they aren't outlined.
Picture
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Possibly caused by MC-166850
Relates to MC-220109.