(Different from *MC-1058)*

If an Armor Stand has the

{Marker:1b}

tag for example:

/summon minecraft:armor_stand ~ ~ ~ {Marker:1b}

If then the player is close to the Armor Stand and approximate to its Y-coordinate and the player is looking in the positive Y-axel (negative in Minecraft, meaning the player is looking up) the Armor Stand stops rendering even if the armor stand is still in the line of sight.

Simplified: Armor stand Markers disappear when looking up even if the armor stand is still in the line of sight

I am pretty sure what is happening is that the game looks at the hitbox of the armor stand and if it is a certain distance away from the players x/y rotation respectively the armor stand and all its contents stop being rendered. This could all be a feature and would explain why MC-1058 hasn't been taken care of but in the case reported above even the armor stand get's unrendered since the hitbox is smaller.