I have had this issue just today where I had to completely recreate my skin, as it seemed to be deleted.and replaced with a default skin.
Steps to reproduce:
1. summon warden
2. cover yourself or a non-warden mob in wool.
3. Wait.
Observed results:
Warden will aggro at the mob.
Expected result:
Warden does not aggro.
I have had this issue just today where I had to completely recreate my skin, as it seemed to be deleted.and replaced with a default skin.