NPC Code:
| X
|---- --- ----
| | | | |
| | | | O|
The player is down the right tunnel, but the baddy is closer to the left tunnel.
The baddy will go down the left tunnel, but zomg, it can't reach the player that way.
Likewise, tunnels that twist or zigzag will cause similar problems.
It's really hard to find a pathing system that will work for any situation.