Very simple steps to reproduce:

• /summon minecraft:vindicator ~ ~1 ~ {PatrolLeader:1b,Patrolling:1b,Johnny:1b}
• summon a Illusioner next to they
• summon a husk next to they
• Wait for the husk to die
  Observe the phenomenon. The Illusioner can see the Husk trying to attack permanently even though it is dead.