City Sqaure Map boss gets "split" by mirage

Bug Report ID: #3.073.917.455
City Sqaure can get split by mirage in a way where 1 of the three bosses is in the mirage and the others arent. In that case the singular boss doesn't move, is invulnerable, doesn't have a hitbox and still counts as being on the map (exarch altars offer boss rewards)
Bug report is from an instance where this happens, Bug is easily reproducible, happens at least once every 10 city square maps