Multiple chests after a single boss

Type of Internet Connection:
ADSL

Internet Connection Speed:
10 Mbits/s (speedtest)

Date & Time:
5 october 2017 at 21h40 UTC

Frequency:
Once (Did not reproduce)

World:
Phoenix

Character Name:
Sarcan Lunys

Monster Name:
Teratotaur

Class/Level:
BLM 70

Party or Solo:
Solo

Race:
Elezen M

In-Game Time:
Unknown

Area and Coordinates:
The sunken temple of Qarn

Steps:
- I entered the dungeon in normal mode as an unsync lvl 70 BLM
- I made my way to the first boss which I fought
- During the fight, I didn't pay attention to the doom debuff the boss put on me
- The moment I killed the boss, doom killed me
- While I was choosing to get back to the entrance, I noticed the reward chest appearing at the same time the boss was reappearing
- I came back to the boss room, and both were still there
- I killed the boss a second time
- A second chest appeared

Screenshots :
https://image.prntscr.com/image/9TFx...rJ_Y_6A3yA.png
https://image.prntscr.com/image/ZiPe...HEeV-qliYw.png