Sometimes the enchanted glint on helmets worn by armor stands disappear if the player stares at nothing, which is air. The glint comes back if the player stares at a block. Only happens if facing west.
Due to the bug introduced in 20w10a which is MC-173747, you are unable to see this as the glint has disappeared.
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It happens in any world. I also realized that it happens if I am facing in the air, and facing at a block would make the enchanted glint to return.
CPU: 4x Intel(R) Core(TM) i3-7130U CPU @ 2.70GHz

Affects 20w06a as well
Also exhibits this behavior on players while not near an armor stand with the same conditions to invoke the bug

Could not replicate in 20w07a, anyone else?

Still an issue in 20w08a.

Affects 20w10a and 20w11a.

This issue seems to be fixed for me. I guess the fix of MC-173747 fixed this as well.
Can anyone confirm that this is still an issue in 20w19a?

Confirmed fixed in 20w19a.

This bug has come back in 1.16.1 and later, most obviously viewed on zombies
I'm unable to reproduce. Does this happen in any world or only in that particular world / location? What's your graphics card?