"Twin" map bosses don't drop loot if killed at the same time

There are a few maps where the map boss contains two entities (e.g., Woodlands with 2 Millers, the new Manor map), and if both are killed at the same time, no loot drops.

I assume there's a race condition happening when both are killed at the exact same moment.

EDIT: Not sure if it affects it, but in all of the cases, the Precursor tablet that empowers the Map boss was used.