Breach monsters didnt generate in encounter

Bug Report ID: #35,162,413

Breach event was the one that you defend npc while she closes breach. In t16 Arachnid Tomb. all doorways cleared and all nodes activated. event started, clicked the meteor storm and no breach monsters are generated and yet waves advanced, at the end obviously no loot dropped but i was awarded 706 graft blood. Not sure how to reproduce and I was definitely not ready to screenshot the encounter...