FINAL FANTASY XI Client Exits With Error on Exiting Legion (Hall of Ki)

Platform: Windows
ISP: Frontier
Type of Internet Connection: FIOS
Internet Connection Speed: 25Mbps/25Mbps
Date & Time: 12/07/2018, ~10:25 PM Pacific Standard Time
Frequency: Always
Character Name: Maledict
Race: TarutaruM
World: Bahamut
Main Job: Dark Knight
Support Job: Samurai
Area and Coordinates: Maquette Abdhaljs - Legion
Party or Solo: Solo
NPC Name: N/A
Monster Name: N/A
Steps:
1. Enter Legion, selecting Hall of Ki.
2. Clear two or more waves in Hall of Ki (It seems to be at least over 20 foes slain).
3. Select the Legion Portal and confirm exit (This is normally done with under ten minutes remaining).
Result:
The FINAL FANTASY XI client displays a "Failed to read data." error before areas are changed ("Downloading Data..." is not shown) and exits back to PlayOnline. It takes several minutes to log back into the game as the server claims to see the character as already logged in. (When I log back in, it's in Rolanberry Fields as if I exited normally.)

Have you tried running a file check?