This skin of a guard changes when he sleeps. When the guard sleeps he close his eyes and taken of his helmet. When a villager blink it will use its sleeping skin. This guard when he blinks his helmet will disappear which is kinda weird. In this photo, I did not caught him blinking without his helmet because it was too fast to be captured by a screenshot.

What you just need to do is change his sleeping skin so that he will not removed his helmet when blinking. I found this problem so that it will not stay in future updates.

Just asking what is Aesthetic?

Aesthetic means preferred looks