When i use this command: 

 

"/execute as @a[nbt={Inventory:[{id:"minecraft:iron_chestplate",tag:{Tags:[IronArmour],display:{Name:"

{\"text\":\"Iron Armour\",\"italic\":false,\"color\":\"gray\",\"bold\":true}

"}}}]}]

run execute as @a[tag=equipeIronArmour] run replaceitem entity @s armor.feet minecraft:iron_boots" 

 

there's a grafical glitch when the boots aren't showing in the slot, but it doesn't happen only with boots, but also with other parts of armour, item is there, but it's not showing up.

Command is in the repeating command block.