If a zombie doesn't see you and you throw something to the side, the zombie will first run to where the noise was, where the thrown object fell, and then, for no reason at all, will run to where the object was thrown from, although there is no reason to run there, and the bug is that the zombie somehow magically understands where the object was thrown from.

Expect:
the zombie runs only to where he heard the noise, where the object fell and tries to find someone there

Actual:
the zombie runs to where the object was thrown, and then runs to where the object was thrown from