I've been using the Mac Beta and for awhile now there has been a bug where an enemy champion portrait appears on the minimap for a brief second, then reappears somewhere else on the map. The champion portrait will briefly appear on the map in the place they were last visible to me, then as they emerge from the fog it will update their position on the minimap to the actual position.
For instance, if Nidalee was last seen at my wolves, then recalls to base, then goes bot, her portrait on the minimap will appear at wolves as she emerges from the fog of war at bot lane, then it will update her location on the map to bot lane. It's very distracting. That's the best I can describe it. It's only a brief moment that it happens but it's very annoying. This only happens with enemy champions.