All monsters killed, but map incomplete -- I believe no rares spawned? (Bug Report ID: #379490574)

Bug Report ID: #379490574

I ran a Rustbowl map and killed every monster in it (it says "0 monsters remain"), without the map being marked complete or remaining rares showing on the minimap at any point. I don't recall killing *any* rares on this map, and suspect they just didn't spawn for some reason?

Map details:
Rustbowl
Monster level: 66
49% increased number of Rare Monsters
Monsters have 56% increased Ailment Threshold
Monsters have 55% increased Stun Threshold
6% increased Rarity of Items found in this Area
85% increased Waystones found in Area