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Date & Time: 23 May 2018, GMT+8 2000 onwards
Frequency: Almost every skill
World name: Tonberry
Character name: Felicia Princess
Retainer name: -
NPC name: -
Monster name: Twintania, Nael, Bahamut
Class/Level: 70
Party or solo: Party
In-game time: GMT+8 2000 hrs
Area and coordinates: Unending Coil of Bahamut, new EX trial
Housing: -
Steps:
1. Use stone 4
2. Sound effect lags for 2-3s
3. Use stone 4
4. Sound effect lags for 2-3s
5. Twintania uses liquid hell
6. Sound effect of last 2-3 liquid hell only appear after 5th puddle has been dropped
7. Lightning debuff on player
8. Lightning sound effect heard 2-3s after debuff resolved
*Add more steps if necessary

Connection Specs
- Type of internet connection/provider: LAN/MyRepublic
- Modem maker/model number: I don't know

Issue was faced by a number of members in my party, not just myself.