Linked monsters falling through the ground

Time: 5:00 AM PST
Frequency: Always
World name: Excalibur
Character name: Vergiliaux Renata
Monster name: Obdella, Dhalmel
Class/Level: WHM53
Party or solo: Party
In-game time: 10:00 AM
Area and coordinates: (24,33)

Steps:

1. I attacked an Obdella with Aero and noticed a Dhalmel from the level above was on my Enemy List. The yellow line indicating these monsters could link was not displayed.
2. In about 5-10 seconds, the linked Dhalmels would slowly fall through the ground and chase you around until disengaged, and then they would disappear back to their spawn point up above.

http://41.media.tumblr.com/798526705...738o1_1280.png