When the player is wearing enchanted armor, has nothing in their hand (both offhand and mainhand must be empty), and in third person view, the enchantment visual on the certain pieces of the armor disappears. When wearing a full set, only the helmet will appear unenchanted, when helmet is removed, the boots will then appear to be unenchanted, when they are removed, the legs will lose theirs, and when they are removed, the chestplate will. If the player is wearing elytra, then the elytra will appear unenchanted, and when removed, the helmet will, then boots, then legs. The same glitch happens with armor stands.

The enchantment visual comes back if the player is a) looking at a block that is close enough to be selected, or b) holding something in their hand.

This appears to be a visual glitch only - when accessing the inventory, the gear keeps its enchants.

Appears to be related to MC-168139, but significant differences (it doesn't matter which way the player is facing), also different version.

Below are screenshots of the bug. It happens in both third person views (front and back). The armor all had protection 4, and the elytra had unbreaking 3. I have tested with several different enchantments, it doesn't appear to matter which one. Also, it is not exclusive to netherite armor.