I've been noticing multiple bugs with armor in the past couple of versions such as whenever players unequip armor/equip armor, it'll still show what they had on when they first joined the world (for example if they joined a world and they had full diamond armor on when joining, but then change it to another type of armor it'll still be diamond),

And another bug I've noticed with armor is that whenever I try to use the /replaceitem
Command to replace my armor to a diamond chest plate it won't show unless I rejoin the world