Monster flickering

On Tonberry server at around 16.12 and 17.12 in Southern Thanalan there is a Rockskin Peiste that is constantly teleporting between two nearby locations.

At first I thought it was flickering in and out, but there is another one close by that appears when this one disappears and vice versa. So it seems to be one entity moving rapidly between two locations.

It can be attacked if you hit it during the split second it's visible before disappearing again, but once it disappears enmity gets reset so half a second later when it comes back it's like a freshly popped mob.

I thought maybe leaving the zone or logging off would fix it, but apparently it's an issue on the server because it's still there today in the same spot.