Shisui of the Violet - Fetters not removing after boss death

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Time: 12:49 am gmt+1
Frequency: Often
World name: Cerberus
Character name: Fei Soulstar
Monster name: Amikiri
Class/Level: Boss / 63
Party or solo: Party
In-game time: 23:49pm
Area and coordinates: Shisui of the violet - First boss arena
Steps:
1. Boss mark someone for his fetters
2. Kill the boss when he trow the fetters or slightly after
3. Boss dead, arena open but fetters do not disappear
*Add more steps if necessary