Abyssal not spawning despite icon on map

Bug Report ID: #501939288

Map: Steppe tier 2 area level 66

Minimap shows the green icon for an Abyssal spawn but there are no mobs.
It is right next to a checkpoint.
It was like that before and after all map rares were killed and it states that the map is completed.

Same just happened on a Crypt map with Ritual, Irradiated and Corrupted, monster level 80.

Bug Report ID: #4221370992