I have noticed, and finally been able to track down an annoying visual glitch that has been occurring on my server. When someone is in the Nether (and perhaps other dimensions), and another person is in the Overworld (again, may or may not work with other dimensions), this bug occurs.

Lets say Player 1 is in the Overworld, Player 2 is in The Nether.

Player 1 will begin to see random Pokeloots appear and disappear on their radar, seemingly at random. Upon going to the location shown by the radar (it helps having the box highlights on), there will be nothing there. It can even be a solid block. As Player 2 moves around in the nether, these "fake" Pokeloots will seem to appear and disappear.

Going over to The Nether with Player 2, at the same coordinates Player 1 found their 'fake' loot at, there will be a REAL pokeloot. Upon Player 2 taking said loot, Player 1 will see their fake/glitched loot from the radar disappear.

To simplify the bug down - If both players are at the same/similar coordinates and chunks as one another, Gameshark will show and highlight Pokeloots that are in another dimension, at the same coordinates.

I am unsure if this requires Player 1 to have visited (and thus, loaded/registered themselves) that location in the other dimension. I was unable to test for that, as in my case as Player 1, I have loaded a whole bunch of the Nether already.