Showdown has finally
fixed the case of Illusions and differing levels, so Illusion behavior, particularly in randbats, may seem different now than what you were used to before. The lead was a L83 Ursaring, and when Zoroark came out, it now correctly appears as a "L78 Ursaring", instead of showing as another L83 like it would have up until a few days ago.
The client's tracking mechanism at this point can account for the presence of both a L83 Ursaring and a L78 Ursaring, which clearly account for two distinct party slots, but there's no telling apart which one's which (unless you know the correlation between a Pokemon's tier and its randbats level), so displaying two Ursarings makes as much sense as any other option there. However, after the illusion is officially broken, putting the Zoroark icon into the last empty slot instead of replacing the second Ursaring with it is clearly a bug. The empty seventh slot icon doesn't appear until the last Pokemon, Aromatisse, makes its presence known, and having it display the icon of an empty slot instead of its own icon is another bug, though probably one that would neatly disappear if the Zoroark icon were properly contained ithin its original slot.