Shinryu & Chelonian Gate (in Hells' Lid) difficult to target using Tab key

Date & Time: Many times, since Stormblood release
Frequency: Very common
World name: Coeurl
Character name: Driskus Blackstone
Retainer name: N/A
NPC name: N/A
Monster name: Chelonian Gate (part of the Genbu battle in Hells' Lid), Shinryu
Class/Level: Any
Party or solo: Party
In-game time: Any
Area and coordinates: Hells' Lid (for Gate), Royal Menagerie (for Shinryu)
Housing: N/A
Steps:
1. Turn camera view to get desired target well into the camera view
2. Press Tab key, most times the target will not be selected despite covering most of the screen.
3. Keep moving camera view and mashing the Tab key, and eventually it'll work if you get the camera view into exactly the right spot.

Target filtering is set correctly so that's not the issue. I'm literally looking directly at the target and cannot select it most of the time. I end up clicking frantically on the name in hopes that it actually works so I can set the Focus Target.