Warmog's Armor bug on Mordekaiser

So I was playing a custom game with Mordekaiser today. I got hit, but my shield negated the damage so I took no health damage. My health regeneration was stopped for some reason. I then noticed every time I took damage, it would cancel Warmog's, even though my health wasn't damaged, only my Iron Man shield was damaged. And even though the health regeneration stopped working when my shield was damaged, but health wasn't damaged, it wouldn't show a cooldown on the item in the inventory slots. Is this intended where if Mordekaiser takes damage to his shield, it stops the health regeneration? I also noticed on Sion that damage taken by Soul Furnace's shield doesn't stop Warmog's regeneration, but damage taken by Mordekaiser's Iron Man shield stops the health regeneration and doesn't show the cooldown of Warmog's in your inventory slots. I know for sure that something is bugged about Warmog's on Mordekaiser, just that is it that Warmog's is supposed to stop its health regeneration on Mordekaiser if he takes damage on his Iron Man shield or is it that Warmog's cooldown won't show in your inventory slots if Mordekaiser takes damage to his Iron Man shield. Basically, Warmog's armor has bugged interactions with Mordekaiser's Iron Man shield. Thank you for reading this and I hope you have a good day!