Isgebind (The Stone Vigil final boss) invisible after returning from the sky

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Date & Time: Approximately 7:23pm AEDT, 5th of February 2024
Frequency: Once
World name: Tonberry
Character name: Ypatia Alethros
Monster name: Isgebind
Class/Level: 90 (synced to The Stone Vigil dungeon level, I can't recall the number but duty finder says level 43)
Party or solo: Party
In-game time: Not sure
Area and coordinates: Stone Vigil ( 11.2 , 6.3)
Housing: Lavender Beds, plot 4, 29th ward, on Tonberry.
Steps:
1. Commenice Isgebind battle (Stone Vigil last boss)
2. Fight until Isgebind flys up into the sky. Wait for the attacks flying accross the arena with a breath of ice (I think that's what it is) to stop.
3. Party members continue to attack after apparently Isgebind returning to the ground, attacks performed by party members, but on my screen there is no Isgebind, and I can't target any enemy.
4. Wait for Isgebind to return to the sky with attacks flying across the arena again, I forget what it's called.
5. Isgebind returns to the ground and is on screen again. Finished duty without further invisibility.

Connection Specs
- Type of internet connection/provider: Mobile (Google Pixel 3) connection via USB with the provider Everyday Mobile From Woolworths, as a mobile prepaid service.
- Modem maker/model number: No modem.

■ PC Specs

Operating system: Windows 10 Pro
Processor: Intel i9 14900 (new)
RAM: 4x16GB (64GB) 6000MHz CL36 DDR5
Graphics Card: GeFroce RTX 3070 8GB
System type: 64-bit operating system, x64-based processor

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Were you zoomed out enough, with enough distance from the wall so that camera wasn't trapped? I know that for wall bosses, for example, if my camera is inside the boss then my ability to click or read the boss information is affected.

I'm not suggesting it didn't happen, but clarifying that it definitely wasn't just a camera that was located inside of Isgebind would be good.

I have seen players disappear before, but it was on a computer where all the RAM was being taken up by other programs, causing unstable behaviour like that. Especially was able to happen on a laptop that shared regular RAM with the graphics processor. I couldn't imagine it happening due to this with 64 GB and a 3070 though.

I tried zooming out and changing camera angle, and running around, but still couldn't see the boss.

Very likely you partially de-synced during the encounter, as what you are describing can happen from sudden changes to data-parity and/or packet loss.

Data parity is the speeds and connection bandwidth differences between data leaving your location, such as the mouse click sent to the server to click the spell icon, vs the same variables being sent from the game server to your PC, such as the spell action happening and the server tells your PC to display the effects. It is different from Ping.
Basically, if the parity is "too different" then stuff gets delayed from registering on your display, because the amount of data going in and out creates a situation were one system (your PC or the game server) is waiting for data to be fully sent or received.
So, if an action requires 100kb of information to be sent to the server and the server has to send a 100kb response, if due to the current condition of the connection in both data directions, is very different, the outgoing 100kb may take longer to send all 100kbs than the same amount incoming (or vice versa more likely) which results in the two systems no longer being in sync with each other and an increasing "delay" in stuff happening on your screen.

Packet Loss can happen, because you are tethering off a cellular device via USB, which can cause issues with the cellular data connection and bandwidth (something happens to pass between your cell device and the tower's line of sight, changing the signal strengths, or Android decides its a great time to check in with Google to upload a bunch of analytics and start pulling in updates or such), the cell tower's load management (the tower suddenly had an increase in current users or such), RF interference (like someone nearby turned on a microwave oven, fired up their Wi-Fi connections, or started a cell phone conversation, and such), USB buss throughput (the computer's USB buss got an increase in data-throughput because other USB devices started using more data bandwidth, so it started throttling your tether or such), the PC decided to use your tether connection for other data related stuff (Windows Update decides you need that new service pack downloaded...... now), and the computer managing the USB port status (PC decides that some USB ports are using too much power, so it lowers the power to them, reducing the port's effectiveness and data handling capacity or such).

The specs of your PC appear to be on the high end of the FF14 system requirements, so I can envision situations were your PC is "running faster" than your connection via the cellular device due to the PC is trying to pull gallons of data through a pipette of a data connection.
Two things that can help mitigate, is to run the FF14 client in a lower "eye candy" settings, so that system resources and data throughput requirements will be a bit lower and to connect the tether to a USB port that is one dedicated to both data and higher power capacity, as your tether is both using the USB port as a data connection and charge power source.