The armor don't drops after the players death, or drops, but with random durability. That looks like zombie/skeleton armor drop chance expends for players, because when you dying by hunger, fall or other thing, and you don't attcked by other player/mob, armor don't drops, but when you dying because damaged by other player(or you can kill yourself with potions with instant damage effect) or by mob, armor have chance be dropped.

I'm tested this on 3 different worlds, all difficults (without peaceful, because there don't spawning agressive mobs), I'm restarting the game, this bug don't disappeared.

Model: Redmi 4x

Manufacturer: Xiaomi