Couldn't find a bug post for this. Unarmored defense is only added when armor and shield not equipped. If I don't have those equipped, AC shows correctly. If I equip the shield, AC goes up by 2. If I equip leather armor, AC stays the same. In all instances, unarmored defense shows the wisdom armor bonus. With shield and/or leather armor equipped, this should go away.  Is there something I'm missing or is this a known, or new bug?

This is as intended. It is afterall, unarmored defense so it only works if you're not wearing armor. 

Can you link the character in question? It's maybe possible that the AC calculation comes out the same and only the display is at issue, but that seems unlikely.

https://www.dndbeyond.com/profile/drkranger0171/characters/33071316

My AC with armor should be 15: leather is 11+dex(+2) + 2 for shield.

With nothing, it should be 16, shown correctly. 

Equip shield with no leather, AC goes to 18. This is wrong. 

Link isn't working, at least not for me. I apologize for my first response, I obviously did not read your post well enough.

I just tried this on my own Monk and it is stacking armor bonuses which, as you said, is wrong.

It's been two years and it still happens, is anyone working on this? Just refresh the AC the same way you make with the unarmed attacks