Big zombie can't climb ladders?

A big zombie that spawns as a guardian of the chest can’t climb stairs and gets stuck when trying to.

Steps to reproduce:

  1. Get a giant zombie spawn with the chest
  2. Aggro the zombie (in my case it aggroed on the goblin camp nearby)
  3. Have his target escape using a ladder

Expected Results:
The zombie either climbs the stairs (clever) or ceases to chase (stupid or too heavy zombie).

Actual Results:
The zombie tries to climb the stairs but gets stuck. He can’t attack and cannot be attacked (hearthlings ignore him even if they are ordered to attack him directly)


Version Number and Mods in use:
A24 new builder, r825

System Information:
Win7 x64