Mirage portal fails to spawn in Racecourse map

Very rarely the mirage encounter gets placed in the inner part of the racing rings of the Racecourse map, where a statue occupies the place of one of the three Afarud minions guarding the captive Djinn or the place Varashta is supposed to spawn once the Afarud minions are defeated. The statue - or the minion despawned by the statue prevents Varashta from appearing, thus no wish can be chosen and no portal will be opened. This happens once every ~1000 maps from my experience.

Bug report reference number: 901 941 375.
Platform: PC, Steam client.