Since my PC group gained horses in one game, the horses always display on top of the PC tokens. Whether the Horses are set to be controllable by All or just the individual players, this happens. If the players are denied control of their mounts, it does not. I see that this was an issue a year or so ago, and code implemented to make PC-sight tokens always on top. These mounts do not have sight, so it's as if this has been reversed!