Castrum Meridianum, bug with third boss

Date & Time: 14.9 around 2-3am (GMT+3)

Frequency: Happened once

Character Name: Sove Stellarum

World: Dungeon instance, doesn't matter

Class/Level: BLM 50

Area and Coordinates: Castrum Meridianum, third boss room

Party or Solo: Party of 8

Monster Name: Magitek Colossus Rubicatus (or something like that)

In-Game Time: Dungeon instance, so it was locked

Steps:
While fighting the boss, after the second wave of adds were slain, the boss suddenly regained its Vulnerability Down buff and got back to half HP, even though there were no Magitek Deathclaws (which Cid kills) in the room. We had no other choice but to wipe because there was no way to remove the buff. This did not happen again.

This may have something to do with the bugged dialogue during the battle. Cid's line is actually spoken by the boss and is said at the beginning of each wave of adds. During my very first run, that "Damn it, that Colossus is enhanced..." line is correctly spoken by Cid and he only said it once. This dialogue error happens every run to everyone.

To avoid this bug dont tank the colossus up the stairs, bring it down close to Cid.