Interestingly, the ship itself doesn't appear on any of the "vessel finder" type websites that I can locate, but if you zoom on the same region on vesselfinder.com, there is a green dashed line box in the same region you've linked here - wonder if that's a naval no-go zone or something? Don't see a legend for it.

> Interestingly, the ship itself doesn't appear on any of the "vessel finder" type websites that I can locate,

Vessel finder & al rely on AIS signal sent by vessel. The AIS beacon probably stopped emitting.

I wondered if that would be the case, it would make sense.

According to a YouTube video (Decaying oil tanker may soon cause one of the largest oil spills ever | DW News) [1] it looks like the box is too much to the south and west.

It's an interesting video which provides a bit of context.

[1] https://www.youtube.com/watch?v=I0fpv9IzZAY