Cast bar not showing up on focus target

Resubmitting this with additional information. Sometimes I don't see a cast bar on the focus target when it's casting a spell. It can get a bit annoying when doing SCOB Turn 1 when the fight get's really hectic. Sometimes I don't notice Rafflesia casting Blight because the cast bar isn't showing up. I don't have any TTL issues and my ping is between 70-80ms.

Type of Internet Connection:
LTE with 70-80ms and no TTL

Internet Connection Speed:
20mbps

Date & Time:
I played in the morning and night server time and it happened a few times

Frequency:
Sometimes. In a fight, there's a small chance that one of the Blights cast by Rafflesia wont show up on the focus cast bar.

Character Name:
Delirium Trigger

Race:
Race of your character when the issue occurred.
Miqote F

World:
Tonberry

Class/Level:
BLM 50

Area and Coordinates:
Second Coil of Bahamut Turn 1

Party or Solo:
Party. I can't identify the party members because I've been with different players.

Monster Name:
Rafflesia

In-Game Time:
Morning and night server time

Steps:
I have restarted my modem a few times but it didn't help. I really have no idea what is causing the issue.